CONSOLIDATED CONDENSED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Millions	Total	Common Stock	Treasury Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive loss
Beginning balance at Dec. 31, 2017	$ 20,572	$ 179	$ (9,168)	$ 7,884	$ 21,935	$ (258)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	1,556				1,556
Other comprehensive income (loss), net of tax	8					8
Dividends on common stock	(1,188)				(1,188)
Issuance of common stock, net	83			83
Purchases of treasury stock	(100)		(100)
Reclassification of stranded tax effects					58	(58)
Ending balance at Jun. 30, 2018	20,931	179	(9,268)	7,967	22,361	(308)
Beginning balance at Mar. 31, 2018	20,722	179	(9,168)	7,916	22,107	(312)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	848				848
Other comprehensive income (loss), net of tax	4					4
Dividends on common stock	(594)				(594)
Issuance of common stock, net	51			51
Purchases of treasury stock	(100)		(100)
Ending balance at Jun. 30, 2018	20,931	179	(9,268)	7,967	22,361	(308)
Beginning balance at Dec. 31, 2018	21,330	179	(10,473)	8,046	23,750	(172)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	1,266				1,266
Other comprehensive income (loss), net of tax	(12)					(12)
Dividends on common stock	(1,168)				(1,168)
Issuance of common stock, net	111			111
Purchases of treasury stock	(180)		(180)
Ending balance at Jun. 30, 2019	21,347	179	(10,653)	8,157	23,848	(184)
Beginning balance at Mar. 31, 2019	21,236	179	(10,653)	8,083	23,795	(168)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	635				635
Other comprehensive income (loss), net of tax	(16)					(16)
Dividends on common stock	(582)				(582)
Issuance of common stock, net	74			74
Ending balance at Jun. 30, 2019	$ 21,347	$ 179	$ (10,653)	$ 8,157	$ 23,848	$ (184)