Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Numerator:
Net income available to common stockholders	$ 409	$ 208	$ 905	$ 593
Denominator:
Denominator for basic earnings per share—weighted-average common shares (in shares)	72,463	72,190	72,419	72,795
Effect of dilutive securities:
Denominator for diluted earnings per share—adjusted weighted-average common shares (in shares)	72,710	72,442	72,678	73,000
Basic earnings per share (in dollars per share)	$ 5.65	$ 2.88	$ 12.49	$ 8.14
Diluted earnings per share (in dollars per share)	$ 5.63	$ 2.87	$ 12.45	$ 8.12
Employee stock options
Effect of dilutive securities:
Effect of dilutive securities (in shares)	4	9	4	12
Restricted stock units
Effect of dilutive securities:
Effect of dilutive securities (in shares)	243	243	255	193