Annual report pursuant to Section 13 and 15(d)

Quarterly Financial Data -- Unaudited (Details)

v3.20.4
Quarterly Financial Data -- Unaudited (Details) - USD ($)
$ / shares in Units, $ in Millions
3 Months Ended 12 Months Ended
Dec. 31, 2020
Sep. 30, 2020
Jun. 30, 2020
Mar. 31, 2020
Dec. 31, 2019
Sep. 30, 2019
Jun. 30, 2019
Mar. 31, 2019
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Quarterly Financial Information Disclosure [Abstract]                      
Revenue $ 2,189 $ 2,025 $ 1,874 $ 1,952 $ 2,062 $ 2,011 $ 1,977 $ 1,744 $ 8,040 $ 7,794 $ 5,771
Cost of services (968) (895) (866) (850) (916) (881) (882) (748)      
Income from operations (503) 478 415 468 399 476 439 333 858 1,647 1,727
Net income $ (677) $ 272 $ 243 $ 293 $ 243 $ 246 $ 263 $ 162 $ 131 $ 914 $ 1,176
Net income per common share--basic ( in USD per share) $ (0.16) $ 0.06 $ 0.06 $ 0.07 $ 0.05 $ 0.06 $ 0.06 $ 0.04 $ 0.03 $ 0.20 $ 0.26
Net income per common share--diluted (in USD per share) $ (0.16) $ 0.06 $ 0.05 $ 0.07 $ 0.05 $ 0.05 $ 0.06 $ 0.03 $ 0.03 $ 0.20 $ 0.26