Condensed Consolidated Statement of Equity - USD ($) shares in Millions, $ in Millions		Total	Common Stock [Member]	6.875% Mandatory Convertible Preferred Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Foreign Currency Adjustment Attributable to Parent [Member]	Dividends/Distributions in Excess of Earnings [Member]
Balance, shares Period Start at Dec. 31, 2017			406
Balance, value Period Start at Dec. 31, 2017		$ 12,339	$ 4	$ 0	$ 16,844	$ (4)	$ (4,505)
Preferred Stock, Shares Outstanding Period Start at Dec. 31, 2017				2
Stock-based compensation related activity, net of forfeitures, value		60			60
Stock-based compensation related activity, net of forfeitures, shares			1
Purchases and retirement of common stock, value		(34)			(34)
Stock Issued During Period, Shares, New Issues			8
Stock Issued During Period, Value, New Issues		841			841
Common stock dividends/distributions	[1]	(876)					(876)
Dividends on preferred stock	[1]	(57)					(57)
Foreign currency translation adjustments	[2]	(1)				(1)
Net income (loss)		294					294
Balance, shares Period End at Jun. 30, 2018			415
Balance, value Period End at Jun. 30, 2018		12,566	$ 4	$ 0	17,711	(5)	(5,144)
Preferred Stock, Shares Outstanding Period End at Jun. 30, 2018				2
Balance, shares Period Start at Mar. 31, 2018			415
Balance, value Period Start at Mar. 31, 2018		12,832	$ 4	$ 0	17,690	(4)	(4,858)
Preferred Stock, Shares Outstanding Period Start at Mar. 31, 2018				2
Stock-based compensation related activity, net of forfeitures, value		24			24
Stock-based compensation related activity, net of forfeitures, shares			0
Purchases and retirement of common stock, value		(1)			(1)
Stock Issued During Period, Shares, New Issues			0
Stock Issued During Period, Value, New Issues		(2)			(2)
Purchases and retirement of common stock, shares			0
Common stock dividends/distributions	[1]	(438)					(438)
Dividends on preferred stock	[1]	(28)					(28)
Foreign currency translation adjustments	[2]	(1)				(1)
Net income (loss)		180					180
Balance, shares Period End at Jun. 30, 2018			415
Balance, value Period End at Jun. 30, 2018		$ 12,566	$ 4	$ 0	17,711	(5)	(5,144)
Preferred Stock, Shares Outstanding Period End at Jun. 30, 2018				2
Balance, shares Period Start at Dec. 31, 2018		415	415
Balance, value Period Start at Dec. 31, 2018		$ 12,034	$ 4	$ 0	17,767	(5)	(5,732)
Preferred Stock, Shares Outstanding Period Start at Dec. 31, 2018		2		2
Stock-based compensation related activity, net of forfeitures, value		$ 77			77
Stock-based compensation related activity, net of forfeitures, shares			1
Purchases and retirement of common stock, value		(43)			(43)
Common stock dividends/distributions	[1]	(944)					(944)
Dividends on preferred stock	[1]	(57)					(57)
Foreign currency translation adjustments		0
Net income (loss)		$ 456					456
Balance, shares Period End at Jun. 30, 2019		416	416
Balance, value Period End at Jun. 30, 2019		$ 11,523	$ 4	$ 0	17,801	(5)	(6,277)
Preferred Stock, Shares Outstanding Period End at Jun. 30, 2019		2		2
Balance, shares Period Start at Mar. 31, 2019			416
Balance, value Period Start at Mar. 31, 2019		$ 11,746	$ 4	$ 0	17,769	(5)	(6,022)
Preferred Stock, Shares Outstanding Period Start at Mar. 31, 2019				2
Stock-based compensation related activity, net of forfeitures, value		33			33
Stock-based compensation related activity, net of forfeitures, shares			0
Purchases and retirement of common stock, value		(1)			(1)
Purchases and retirement of common stock, shares			0
Common stock dividends/distributions	[1]	(473)					(473)
Dividends on preferred stock	[1]	(28)					(28)
Foreign currency translation adjustments		0
Net income (loss)		$ 246					246
Balance, shares Period End at Jun. 30, 2019		416	416
Balance, value Period End at Jun. 30, 2019		$ 11,523	$ 4	$ 0	$ 17,801	$ (5)	$ (6,277)
Preferred Stock, Shares Outstanding Period End at Jun. 30, 2019		2		2

[1] See note 7 for information regarding common and preferred stock dividends declared per share.

[2] See the condensed consolidated statement of operations and other comprehensive income (loss) for the components of other comprehensive income (loss).