Debt - Notes Repurchased (Details) $ in Millions	3 Months Ended
	Mar. 31, 2020 USD ($)
Long-Term Debt Instrument [Line Items]
Debt instrument, repurchased face amount	$ 156
Senior notes
Long-Term Debt Instrument [Line Items]
Debt instrument, repurchased face amount	156
Debt repurchased, principal	93
Gain on repurchase of debt	63
Senior notes | 6.625% senior notes due 2020
Long-Term Debt Instrument [Line Items]
Debt instrument, repurchased face amount	31
Senior notes | 6.875% senior notes due 2020
Long-Term Debt Instrument [Line Items]
Debt instrument, repurchased face amount	17
Senior notes | 6.125% senior notes due 2021
Long-Term Debt Instrument [Line Items]
Debt instrument, repurchased face amount	66
Senior notes | 5.375% senior notes due 2021
Long-Term Debt Instrument [Line Items]
Debt instrument, repurchased face amount	$ 42