Equity Stock Repurchases - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2020	Feb. 22, 2019	Feb. 26, 2018	Feb. 23, 2017	Feb. 24, 2016
Stock Repurchases [Line Items]
Shares Repurchased and Retired During Period, Shares	1.2
Shares Repurchased and Retired During Period, Value	$ 20
Weighted Average Market Price of Shares Repurchased and Retired During Period	$ 17.21
Stock Repurchase Program, Remaining Authorized Repurchase Amount		$ 204
Maximum | 2016 Stock Repurchase Plan
Stock Repurchases [Line Items]
Shares Authorized under Stock Repurchase Program,						$ 275
Maximum | 2017 Stock Repurchase Plan
Stock Repurchases [Line Items]
Shares Authorized under Stock Repurchase Program,					$ 300
Maximum | 2018 Stock Repurchase Plan
Stock Repurchases [Line Items]
Shares Authorized under Stock Repurchase Program,				$ 350
Maximum | 2019 Stock Repurchase Plan
Stock Repurchases [Line Items]
Shares Authorized under Stock Repurchase Program,			$ 175