CONSOLIDATED CONDENSED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Millions	Total	Common Stock	Preferred Stock	Treasury Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Loss	Non-controlling Interests
Beginning balance at Dec. 31, 2017	$ 20,572	$ 179	$ 0	$ (9,168)	$ 7,884	$ 21,935	$ (258)	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	3,425					3,425
Other comprehensive income (loss), net of tax	161						161
Dividends on common stock	(1,783)					(1,783)
Issuance of common stock and other, net	107				107
Purchases of treasury stock	(994)			(994)
Reclassification of stranded tax effects						58	(58)
Noncontrolling interest contributions, net	0							0
Ending balance at Sep. 30, 2018	21,488	179	0	(10,162)	7,991	23,635	(155)	0
Beginning balance at Jun. 30, 2018	20,931	179	0	(9,268)	7,967	22,361	(308)	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	1,869					1,869
Other comprehensive income (loss), net of tax	153						153
Dividends on common stock	(595)					(595)
Issuance of common stock and other, net	24	0			24
Purchases of treasury stock	(894)			(894)
Reclassification of stranded tax effects						0	0
Noncontrolling interest contributions, net	0							0
Ending balance at Sep. 30, 2018	21,488	179	0	(10,162)	7,991	23,635	(155)	0
Beginning balance at Dec. 31, 2018	21,330	179	0	(10,473)	8,046	23,750	(172)	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	514					472		42
Other comprehensive income (loss), net of tax	(160)						(160)
Dividends on common stock	(1,877)					(1,877)
Dividends on preferred stock	(118)					(118)
Issuance of common stock and other, net	6,851	30			6,821
Issuance of preferred stock, net	9,762		9,762
Purchases of treasury stock	(180)			(180)
Fair value of noncontrolling interest acquired	4,875							4,875
Noncontrolling interest contributions, net	8							8
Ending balance at Sep. 30, 2019	41,005	209	9,762	(10,653)	14,867	22,227	(332)	4,925
Beginning balance at Jun. 30, 2019	21,347	179	0	(10,653)	8,157	23,848	(184)	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(752)					(794)		42
Other comprehensive income (loss), net of tax	(148)						(148)
Dividends on common stock	(709)					(709)
Dividends on preferred stock	(118)					(118)
Issuance of common stock and other, net	6,740	30			6,710
Issuance of preferred stock, net	9,762		9,762
Fair value of noncontrolling interest acquired	4,875							4,875
Noncontrolling interest contributions, net	8							8
Ending balance at Sep. 30, 2019	$ 41,005	$ 209	$ 9,762	$ (10,653)	$ 14,867	$ 22,227	$ (332)	$ 4,925