Loans Loans (Troubled Debt Restructurings Subsequent Default) (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017 USD ($) loan	Sep. 30, 2016 USD ($) loan	Sep. 30, 2017 USD ($) loan	Sep. 30, 2016 USD ($) loan
Financing Receivable, Modifications [Line Items]
Number of loans modified as a troubled debt restructuring	0	5	0	7
Payment Default [Member]
Financing Receivable, Modifications [Line Items]
Number of loans modified as a troubled debt restructuring	0	3	2	7
Recorded investment on TDR modifications with payment default | $	$ 0.0	$ 6.6	$ 1.6	$ 6.7