Condensed Consolidated Statements of Shareholders' Equity - USD ($) $ in Millions	Total	Common Stock	Preferred Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Retained Earnings
Balance at beginning of period at Dec. 31, 2020	$ 13,598	$ 0	$ 0	$ 8,642	$ (1,309)	$ 6,265
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	878					878
Other comprehensive income (loss)	(23)				(23)
Stock-based compensation	8			8
Dividends paid (Note 10)	(661)					(661)
Balance at end of period at Mar. 31, 2021	13,800	0	0	8,650	(1,332)	6,482
Balance at beginning of period at Dec. 31, 2021	13,794	0	0	8,692	(1,273)	6,375
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	962					962
Other comprehensive income (loss)	238				238
Stock-based compensation	10			10
Balance at end of period at Mar. 31, 2022	$ 15,004	$ 0	$ 0	$ 8,701	$ (1,034)	$ 7,337