Annual report pursuant to Section 13 and 15(d)

Employee Benefit Plans (Details)

v3.10.0.1
Employee Benefit Plans (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Employee Benefit Plans [Abstract]      
Employer cash contributions $ 26 $ 20 $ 25