Variable Interest Entities (Narrative) (Details) - USD ($)	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Tax Credit Structures
Variable Interest Entity [Line Items]
Carrying amounts	$ 178,100,000		$ 186,500,000
Exposure to loss from liquidity arrangements and obligations to purchase assets	0
Liabilities related to undrawn commitments	54,600,000		56,700,000
Affordable housing tax credits and other tax benefits	12,100,000	$ 12,000,000
Leveraged Leasing Transactions
Variable Interest Entity [Line Items]
Carrying amounts	145,900,000		$ 183,500,000
Exposure to loss from liquidity arrangements and obligations to purchase assets	$ 0
Leveraged Leasing Transactions | Lower Limit
Variable Interest Entity [Line Items]
Funding of assets cost via equity interest	20.00%
Funding of asset's cost via third party non recourse debt holders	70.00%
Leveraged Leasing Transactions | Upper Limit
Variable Interest Entity [Line Items]
Funding of assets cost via equity interest	30.00%
Funding of asset's cost via third party non recourse debt holders	80.00%
Accounting Standards Update 2015-02
Variable Interest Entity [Line Items]
Money market mutual funds fees waived	$ 200,000	$ 7,700,000