Consolidated Statements of Stockholders' Equity - USD ($) $ in Millions	Total	Common Stock	Treasury Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Loss
Balance at Dec. 31, 2015	$ 24,350	$ 178	$ (9,121)	$ 7,640	$ 25,960	$ (307)
Increase (Decrease) in Stockholders' Equity
Net income (loss)	(574)				(574)
Other comprehensive income, net of tax	41					41
Dividends on common stock	(2,405)				(2,405)
Issuance of common stock and other, net	107			107
Purchases of treasury stock	(22)		(22)
Balance at Dec. 31, 2016	21,497	178	(9,143)	7,747	22,981	(266)
Increase (Decrease) in Stockholders' Equity
Net income (loss)	1,311				1,311
Other comprehensive income, net of tax	8					8
Dividends on common stock	(2,357)				(2,357)
Issuance of common stock and other, net	138	1		137
Purchases of treasury stock	(25)		(25)
Balance at Dec. 31, 2017	20,572	179	(9,168)	7,884	21,935	(258)
Increase (Decrease) in Stockholders' Equity
Net income (loss)	4,131				4,131
Other comprehensive income, net of tax	144					144
Dividends on common stock	(2,374)				(2,374)
Issuance of common stock and other, net	162			162
Purchases of treasury stock	(1,305)		(1,305)
Reclassification of stranded tax effects					58	(58)
Balance at Dec. 31, 2018	$ 21,330	$ 179	$ (10,473)	$ 8,046	$ 23,750	$ (172)