Condensed Consolidated Statements of Stockholders' Equity (Unaudited) - USD ($)	Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Treasury Stock
Total stockholder's equity at beginning of period at Dec. 31, 2017		$ 683,000,000	$ 2,175,000,000	$ 9,364,000,000	$ 16,000,000	$ (60,000,000)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation			(2,000,000)			1,000,000
Dividends to common stockholders ($2.35 and $2.30 per share)				(627,000,000)
Net income	$ 291,000,000			291,000,000
Other comprehensive income (loss)	(416,000,000)				(416,000,000)
Purchase of treasury stock						0
Total stockholder's equity at end of period at Mar. 31, 2018	11,425,000,000	683,000,000	2,173,000,000	9,028,000,000	(400,000,000)	(59,000,000)
Total stockholder's equity at beginning of period at Dec. 31, 2017		683,000,000	2,175,000,000	9,364,000,000	16,000,000	(60,000,000)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Purchase of treasury stock	0
Total stockholder's equity at end of period at Dec. 31, 2018	11,217,000,000	683,000,000	2,192,000,000	9,277,000,000	(878,000,000)	(57,000,000)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation			(8,000,000)			7,000,000
Dividends to common stockholders ($2.35 and $2.30 per share)				(643,000,000)
Net income	342,000,000			342,000,000
Other comprehensive income (loss)	554,000,000				554,000,000
Purchase of treasury stock	(14,000,000)					(14,000,000)
Total stockholder's equity at end of period at Mar. 31, 2019	$ 11,455,000,000	$ 683,000,000	$ 2,184,000,000	$ 8,976,000,000	$ (324,000,000)	$ (64,000,000)