Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Numerator:
Net income available to common stockholders	$ 481	$ 409	$ 293	$ 203	$ 297	$ 208	$ 212	$ 173	$ 1,386	$ 890	$ 1,174
Denominator:
Denominator for basic earnings per share—weighted-average common shares (in shares)									72,432	72,658	77,341
Effect of dilutive securities:
Denominator for diluted earnings per share—adjusted weighted-average common shares (in shares)									72,817	72,929	77,710
Basic earnings per share (in dollars per share)	$ 6.65	$ 5.65	$ 4.03	$ 2.81	$ 4.11	$ 2.88	$ 2.94	$ 2.33	$ 19.14	$ 12.24	$ 15.18
Diluted earnings per share (in dollars per share)	$ 6.61	$ 5.63	$ 4.02	$ 2.80	$ 4.09	$ 2.87	$ 2.93	$ 2.33	$ 19.04	$ 12.20	$ 15.11
Employee stock options
Effect of dilutive securities:
Share-based payment arrangements (in shares)									4	12	114
Restricted stock units
Effect of dilutive securities:
Share-based payment arrangements (in shares)									381	259	255