Condensed Consolidated Statements of Stockholders' Equity (Unaudited) - USD ($) $ in Millions	Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive (Loss) Income	Treasury Stock	Previously Reported Retained Earnings	Previously Reported Accumulated Other Comprehensive (Loss) Income
Total stockholder's equity at beginning of period at Dec. 31, 2018		$ 683	$ 2,192		$ (878)	$ (57)	$ 9,277	$ (878)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation			(8)			7
Dividends to common stockholders ($2.37 and $2.35 per share)				$ (643)
Net (loss) income	$ 342			342
Other comprehensive (loss) income	554				554
Purchase of treasury stock	(14)					(14)
Total stockholder's equity at end of period at Mar. 31, 2019	11,455	683	2,184	8,976	(324)	(64)
Total stockholder's equity at beginning of period at Dec. 31, 2019	12,215	683	2,203		51	(70)	$ 9,348	$ 51
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation			(16)			16
Dividends to common stockholders ($2.37 and $2.35 per share)				(648)
Net (loss) income	(61)			(61)
Other comprehensive (loss) income	(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)