Consolidated Statements of Stockholders' Equity - USD ($) $ in Millions	Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Treasury Stock	Previously Reported Retained Earnings	Previously Reported Accumulated Other Comprehensive Income (Loss)
Total stockholder's equity at beginning of period at Dec. 31, 2016		$ 683	$ 2,173			$ (73)	$ 9,359	$ (173)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation			2			13
Dividends to common stockholders ($3.40, $3.30, and $3.10 per share)				$ (844)
Net income	$ 899			899
Other comprehensive income (loss)	205				$ 205
Total stockholder's equity at end of period at Dec. 31, 2017	12,244	683	2,175	9,414	32	(60)	9,414	32
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation			17			3
Dividends to common stockholders ($3.40, $3.30, and $3.10 per share)				(900)
Net income	813			813
Other comprehensive income (loss)	(894)				(894)
Total stockholder's equity at end of period at Dec. 31, 2018	11,217	683	2,192	9,277	(878)	(57)	$ 9,277	$ (878)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation			11			10
Dividends to common stockholders ($3.40, $3.30, and $3.10 per share)				(929)
Net income	1,000			1,000
Other comprehensive income (loss)	929				929
Purchase of treasury stock						(23)
Total stockholder's equity at end of period at Dec. 31, 2019	$ 12,215	$ 683	$ 2,203	$ 9,348	$ 51	$ (70)