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Long-Term Debt and Interest Rate Swap Arrangements (Narrative) (Details) (USD $)
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3 Months Ended | 12 Months Ended | 12 Months Ended | |||||||||||||||||||||
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Mar. 31, 2013
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Mar. 31, 2012
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Sep. 30, 2009
item
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Dec. 31, 2011
item
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Dec. 31, 2010
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Dec. 31, 2012
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Sep. 02, 2010
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Dec. 31, 2012
Pay fixed and receive variable 3 month LIBOR
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Dec. 31, 2012
Pay variable 3 month LIBOR and receive fixed
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Mar. 31, 2013
7.125% Senior Secured Notes due 2017
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Dec. 31, 2012
7.125% Senior Secured Notes due 2017
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Dec. 31, 2011
7.125% Senior Secured Notes due 2017
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Mar. 23, 2010
7.125% Senior Secured Notes due 2017
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Mar. 31, 2013
7.5% Senior Secured Notes due 2019, net of original issue discount
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Dec. 31, 2012
7.5% Senior Secured Notes due 2019, net of original issue discount
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Dec. 31, 2011
7.5% Senior Secured Notes due 2019, net of original issue discount
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Sep. 25, 2009
7.5% Senior Secured Notes due 2019, net of original issue discount
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Mar. 31, 2013
7.375% Senior Secured Notes due 2020
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Dec. 31, 2012
7.375% Senior Secured Notes due 2020
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Dec. 31, 2011
7.375% Senior Secured Notes due 2020
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Mar. 23, 2010
7.375% Senior Secured Notes due 2020
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Mar. 31, 2013
5.125% Senior Secured Notes due 2022
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Dec. 31, 2012
5.125% Senior Secured Notes due 2022
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Jul. 02, 2012
5.125% Senior Secured Notes due 2022
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| Debt Instrument [Line Items] | ||||||||||||||||||||||||
| Debt and capital lease obligations | $ 3,596,000,000 | $ 2,490,000,000 | $ 3,477,000,000 | $ 376,000,000 | $ 500,000,000 | $ 500,000,000 | $ 500,000,000 | $ 760,000,000 | $ 988,000,000 | $ 986,000,000 | $ 1,000,000,000 | $ 500,000,000 | $ 500,000,000 | $ 500,000,000 | $ 500,000,000 | $ 500,000,000 | $ 500,000,000 | $ 500,000,000 | ||||||
| Debt instrument interest rate stated percentage | 7.125% | 7.125% | 7.50% | 7.50% | 7.375% | 7.375% | 5.125% | 5.125% | ||||||||||||||||
| Debt issuance price percentage | 98.278% | |||||||||||||||||||||||
| Line of credit facility maximum borrowing capacity | 2,000,000,000 | 2,000,000,000 | ||||||||||||||||||||||
| Line of credit facility standby letter of credit | 250,000,000 | 250,000,000 | ||||||||||||||||||||||
| Debt instrument lower range of basis spread on variable rate | 0.25% | 0.50% | ||||||||||||||||||||||
| Debt instrument higher range of basis spread on variable rate | 2.00% | 3.00% | ||||||||||||||||||||||
| Line of credit facility remaining borrowing capacity | 1,700,000,000 | 1,100,000,000 | ||||||||||||||||||||||
| Five year maturities | ||||||||||||||||||||||||
| 2013 | 0 | |||||||||||||||||||||||
| 2014 | 0 | |||||||||||||||||||||||
| 2015 | 903,000,000 | |||||||||||||||||||||||
| 2016 | 0 | |||||||||||||||||||||||
| 2017 | 500,000,000 | |||||||||||||||||||||||
| Number of interest rate swap arrangements entered into by the entity | 7 | 7 | ||||||||||||||||||||||
| Notional amount of interest rate swap arrangements | 1,800,000,000 | 1,400,000,000 | ||||||||||||||||||||||
| Fixed interest rate, minimum (as a percent) | 2.98% | 0.57% | ||||||||||||||||||||||
| Fixed interest rate, maximum (as a percent) | 3.67% | 0.95% | ||||||||||||||||||||||
| Variable rate basis | 3 month LIBOR | 3 month LIBOR | ||||||||||||||||||||||
| Variable interest rate (as a percent) | 0.31% | 0.31% | ||||||||||||||||||||||
| Interest rate derivatives at fair value net | 59,000,000 | 12,000,000 | ||||||||||||||||||||||
| Interest rate derivative liabilities at fair value | 61,000,000 | 13,000,000 | ||||||||||||||||||||||
| Interest rate derivative assets at fair value | 2,000,000 | 1,000,000 | ||||||||||||||||||||||
| Outstanding letters of credit | 37,000,000 | 30,000,000 | ||||||||||||||||||||||
| Loss on extinguishment of debt | $ (41,000,000) | $ 0 | $ 22,000,000 | |||||||||||||||||||||
| Debt weighted average interest rate | 5.80% | 7.00% | ||||||||||||||||||||||