Series A Convertible Preferred Stock (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019	Sep. 18, 2019	Mar. 17, 2017	Dec. 04, 2015
Class of Stock [Line Items]
Series A convertible preferred stock, issued (in shares)	400,000		400,000		400,000
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
Preferred stock, par value (in dollars per share)								$ 1,000
Direct issuance expenses								$ 26
Dividend rate								5.50%
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
Preferred Shares Converted into Common Stock in Redemption					9,160,000
Dividends, Preferred Stock, Cash	$ 6
Dividends, preferred stock, paid-in-kind	7	$ 12	$ 7	$ 24
Dividends, Preferred Stock			13
Accrued Dividends	$ 1		$ 1		$ 1
Financial instruments subject to redemption, settlement terms, maximum number of shares (in shares)	13,500,000		13,500,000		13,300,000