Series A Convertible Preferred Stock (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Sep. 18, 2019	Dec. 31, 2018	Mar. 17, 2017	Dec. 04, 2015
Class of Stock [Line Items]
Series A convertible preferred stock, issued (in shares)	300,000		300,000			800,000
Deemed Dividend on Preferred Stock Redemption	$ 67,000,000	$ 0	$ 67,000,000	$ 0
Secondary offering by the preferred shareholders							342,000
Redeemed Shares of Preferred Stock							90,000
Repurchase price per share of common stock upon conversion							$ 48.47
Series A Convertible Preferred Stock
Class of Stock [Line Items]
Series A convertible preferred stock, issued (in shares)								820,000
Aggregate purchase price of preferred shares								$ 820,000,000
Preferred stock, par value (in dollars per share)								$ 1,000
Direct issuance expenses								$ 26,000,000
Dividend rate								5.50%
Dividends, preferred stock, paid-in-kind	13,000,000	$ 11,000,000	37,000,000	34,000,000
Accrued dividends	$ 1,000,000		1,000,000			$ 3,000,000
Payments of Dividends			$ 0	$ 0
Conversion price per share at option of holder (in dollars per share)								$ 30.00
Conversion rate per preferred share (in shares)			33.333
Redeemed Shares of Preferred Stock					512,221
Blackstone Shares Converted into Common Shares					237,673
Cash Paid for the Redemption of Preferred Stock					$ 302,000,000
Preferred Shares Converted into Common Stock in Redemption			9,160,000
Financial instruments subject to redemption, settlement terms, maximum number of shares (in shares)	13,100,000		13,100,000			29,000,000.0
Common Stock [Member]
Class of Stock [Line Items]
Preferred Shares Converted into Common Stock in Redemption	9,000,000