Fair Value Measurements (Narrative) (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2016	Dec. 31, 2015	Dec. 31, 2016
Finite-Lived Intangible Assets [Line Items]
Fair value of loan servicing rights		$ 3.7	$ 4.2
Mortgage Servicing Rights (MSR) Impairment (Recovery)	$ 0.6	0.1
Noncovered [Member]
Finite-Lived Intangible Assets [Line Items]
Noncovered impaired loans carrying amount		25.9	19.7
Noncovered impaired loans measured at fair value		21.6	13.2
Noncovered impaired loans life to date impairment		4.3	$ 6.5
Impairment charge of other real estate assets		$ 0.1