Derivative Instruments (Narrative) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2020	Jun. 30, 2020	Dec. 31, 2019	Dec. 13, 2019	Dec. 12, 2019	Nov. 21, 2016
Derivative [Line Items]
Class of Warrant or Right, Number of Securities Called by Each Warrant or Right				84,500,000		7,777,779
Class of Warrant or Right, Exercise Price of Warrants or Rights				$ 6.43	$ 99.96	$ 99.96
Additional Paid in Capital, Common Stock			$ 2,897		$ 2,897
Warrant Fair Value Adjustment		$ (70)
Class of Warrant or Right, Unissued								1
Warrant [Member]
Derivative [Line Items]
Additional Paid in Capital, Common Stock						$ 31
Interest Rate Swap [Member] | Fair Value Hedging [Member]
Derivative [Line Items]
Deferred (Gain) Loss on Discontinuation of Fair Value Hedge		$ (8)	0		0	$ 0	$ 0
Foreign currency forward contracts [Member]
Derivative [Line Items]
Notional amount			$ 337		$ 389
Additional Paid-in Capital [Member]
Derivative [Line Items]
Stock Issued During Period, Shares, New Issues	84,500,000