Long-Term Debt - Redemption of Senior Notes (Details) - USD ($)				3 Months Ended	12 Months Ended
	Sep. 11, 2020	Jul. 15, 2020	Aug. 25, 2019	Dec. 31, 2019	Dec. 31, 2020	Dec. 31, 2019
Senior notes
Debt Instrument [Line Items]
Gain from extinguishment of debt					$ 27,000,000	$ 5,000,000
Senior notes | 5.625% Senior notes due 2023
Debt Instrument [Line Items]
Amount of debt redeemed	$ 140,000,000	$ 360,000,000
Stated interest rate	5.625%	5.625%
Senior notes | 5.125% Senior notes due 2023
Debt Instrument [Line Items]
Amount of debt redeemed	$ 700,000,000
Stated interest rate	5.125%
Senior notes | 5.375% Senior notes due 2022
Debt Instrument [Line Items]
Amount of debt redeemed		$ 840,000,000		$ 160,000,000
Stated interest rate		5.375%		5.375%		5.375%
Senior notes | 6.125% Senior Notes due 2021
Debt Instrument [Line Items]
Amount of debt redeemed			$ 400,000,000	$ 240,000,000
Stated interest rate			6.125%	6.125%		6.125%
Senior notes | 5.750% Senior notes due 2022
Debt Instrument [Line Items]
Amount of debt redeemed				$ 600,000,000
Stated interest rate				5.75%		5.75%