Condensed Consolidated Statements of Stockholders' Equity (Unaudited) - USD ($) $ in Millions	Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Retained Earnings Cumulative effect adjustments from changes in accounting guidance, net of tax	Retained Earnings Balance, beginning of period, as adjusted	Accumulated Other Comprehensive Income (Loss)	Treasury Stock
Total stockholder's equity at beginning of period at Dec. 31, 2019		$ 683	$ 2,203	$ 9,348	$ (5)	$ 9,343	$ 51	$ (70)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation			(16)					16
Dividends to common stockholders ($1.13 and $2.37 per share)				(648)
Net income (loss)	$ (61)			(61)
Other comprehensive loss	(1,121)						(1,121)
Purchase of treasury stock	(18)							(18)
Total stockholder's equity at end of period at Mar. 31, 2020	10,362	683	2,187	8,634			(1,070)	(72)
Total stockholder's equity at beginning of period at Dec. 31, 2020	12,707	683	2,211	9,081	$ 0	$ 9,081	803	(71)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation			(17)					15
Dividends to common stockholders ($1.13 and $2.37 per share)				(309)
Net income (loss)	312			312
Other comprehensive loss	(616)						(616)
Purchase of treasury stock	(3)							(3)
Total stockholder's equity at end of period at Mar. 31, 2021	$ 12,089	$ 683	$ 2,194	$ 9,084			$ 187	$ (59)