Variable Interest Entities (Narrative) (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Variable Interest Entity [Line Items]
Unfunded commitment related to seed capital investments	$ 0		$ 0		$ 25,000,000
Tax Credit Structures
Variable Interest Entity [Line Items]
Carrying amounts	165,100,000		165,100,000		173,500,000
Exposure to loss from liquidity arrangements and obligations to purchase assets	0		0
Liabilities related to undrawn commitments	32,200,000		32,200,000		10,500,000
Affordable housing tax credits and other tax benefits	12,500,000	$ 13,100,000	36,500,000	$ 39,600,000
Leveraged Leasing Transactions
Variable Interest Entity [Line Items]
Carrying amounts	193,500,000		193,500,000		389,400,000
Exposure to loss from liquidity arrangements and obligations to purchase assets	$ 0		$ 0
Leveraged Leasing Transactions | Lower Limit
Variable Interest Entity [Line Items]
Funding of asset's cost via an equity interest	20.00%		20.00%
Funding of asset's cost via third party non recourse debt holders	70.00%		70.00%
Leveraged Leasing Transactions | Upper Limit
Variable Interest Entity [Line Items]
Funding of asset's cost via an equity interest	30.00%		30.00%
Funding of asset's cost via third party non recourse debt holders	80.00%		80.00%
Other Assets
Variable Interest Entity [Line Items]
Investments valued using net asset value per share	$ 0		$ 0		$ 25,300,000
Accounting Standards Update 2015-02
Variable Interest Entity [Line Items]
Money market mutual funds fees waived	$ 200,000		$ 8,100,000