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		36			36
Stock-based compensation related activity, net of forfeitures, shares			1
Purchases and retirement of common stock, value		(33)			(33)
Stock Issued During Period, Shares, New Issues			8
Stock Issued During Period, Value, New Issues		843			843
Purchases and retirement of common stock, shares			0
Other comprehensive income (loss)	[1]	0
Common stock dividends/distributions	[2]	(439)					(439)
Dividends on preferred stock	[2]	(28)					(28)
Net income (loss)		114					114
Balance, shares Period End at Mar. 31, 2018			415
Balance, value Period End at Mar. 31, 2018		$ 12,832	$ 4	$ 0	17,690	(4)	(4,858)
Preferred Stock, Shares Outstanding Period End at Mar. 31, 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		$ 44			44
Stock-based compensation related activity, net of forfeitures, shares			1
Purchases and retirement of common stock, value		(42)			(42)
Stock Issued During Period, Shares, New Issues			0
Stock Issued During Period, Value, New Issues		0			0
Purchases and retirement of common stock, shares			0
Other comprehensive income (loss)	[1]	0
Common stock dividends/distributions	[2]	(472)					(472)
Dividends on preferred stock	[2]	(28)					(28)
Net income (loss)		$ 210					210
Balance, shares Period End at Mar. 31, 2019		416	416
Balance, value Period End at Mar. 31, 2019		$ 11,746	$ 4	$ 0	$ 17,769	$ (5)	$ (6,022)
Preferred Stock, Shares Outstanding Period End at Mar. 31, 2019		2		2

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

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