Equity - Capital Purchase Program Warrants (Details) - USD ($) shares in Millions, $ in Millions	1 Months Ended	3 Months Ended			6 Months Ended	9 Months Ended
	Oct. 30, 2019	Sep. 30, 2019	Jun. 30, 2019	Sep. 30, 2018	Jun. 30, 2019	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Class of Warrant or Right [Line Items]
Warrants outstanding								1.9
Treasury Stock, Shares, Acquired		1.1	0.5		1.6
Treasury Stock, Value, Acquired, Cost Method		$ 63	$ 27		$ 90
Subsequent Event [Member]
Class of Warrant or Right [Line Items]
Treasury Stock, Shares, Acquired	0.6
Treasury Stock, Value, Acquired, Cost Method	$ 36
Warrant [Member]
Class of Warrant or Right [Line Items]
Warrants Exercised				0.1		1.9	0.2