Summary of Significant Accounting Policies - Computation of Basic and Diluted Earnings Per Common Share (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Earnings Per Share [Abstract]
Net income available to common shareholders	$ 563	$ 478	$ 362
Less: Dividends paid on and earnings allocated to participating securities	(7)	(6)	(4)
Earnings applicable to common stock	$ 556	$ 472	$ 358
Weighted average common shares outstanding	463,865,661	462,605,341	465,380,010
Basic earnings per common share	$ 1.20	$ 1.02	$ 0.77
Earnings applicable to common stock	$ 556	$ 472	$ 358
Potential dilutive common shares	767,058	676,061	283,322
Total shares for diluted earnings per common share computation	464,632,719	463,281,402	465,663,332
Diluted earnings per common share and common share equivalents	$ 1.20	$ 1.02	$ 0.77