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			11,000,000			2,000,000
Dividends to common stockholders ($0.35, $0.35, $3.05 and $2.95 per share)				(805,000,000)
Net income	$ 897,000,000			897,000,000
Other comprehensive income (loss)	(773,000,000)				(773,000,000)
Purchase of treasury stock						0
Total stockholder's equity at end of period at Sep. 30, 2018	11,510,000,000	683,000,000	2,186,000,000	9,456,000,000	(757,000,000)	(58,000,000)
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)
Total stockholder's equity at beginning of period at Jun. 30, 2018		683,000,000	2,179,000,000	9,216,000,000	(605,000,000)	(58,000,000)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation			7,000,000			0
Dividends to common stockholders ($0.35, $0.35, $3.05 and $2.95 per share)				(96,000,000)
Net income	336,000,000			336,000,000
Other comprehensive income (loss)	(152,000,000)				(152,000,000)
Purchase of treasury stock						0
Total stockholder's equity at end of period at Sep. 30, 2018	11,510,000,000	683,000,000	2,186,000,000	9,456,000,000	(757,000,000)	(58,000,000)
Total stockholder's equity at beginning 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			5,000,000			8,000,000
Dividends to common stockholders ($0.35, $0.35, $3.05 and $2.95 per share)				(833,000,000)
Net income	727,000,000			727,000,000
Other comprehensive income (loss)	1,017,000,000				1,017,000,000
Purchase of treasury stock	(18,000,000)					(18,000,000)
Total stockholder's equity at end of period at Sep. 30, 2019	12,123,000,000	683,000,000	2,197,000,000	9,171,000,000	139,000,000	(67,000,000)
Total stockholder's equity at beginning of period at Jun. 30, 2019		683,000,000	2,190,000,000	9,159,000,000	120,000,000	(65,000,000)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation			7,000,000			0
Dividends to common stockholders ($0.35, $0.35, $3.05 and $2.95 per share)				(95,000,000)
Net income	107,000,000			107,000,000
Other comprehensive income (loss)	19,000,000				19,000,000
Purchase of treasury stock						(2,000,000)
Total stockholder's equity at end of period at Sep. 30, 2019	$ 12,123,000,000	$ 683,000,000	$ 2,197,000,000	$ 9,171,000,000	$ 139,000,000	$ (67,000,000)