Consolidations and Transfers of Financial Assets Types of VIEs (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Variable Interest Entities [Line Items]
Carrying value of LIHTC partnership investments	$ 0
Consolidated VIEs [Member]
Variable Interest Entities [Line Items]
Variable Interest Entity, Conclusion to Consolidate, Change in Facts and Circumstances, Amount	$ 17,000,000
Unconsolidated VIEs [Member]
Variable Interest Entities [Line Items]
Variable Interest Entity, Conclusion to Consolidate, Change in Facts and Circumstances, Amount		$ 258,000,000