Goodwill, Core Deposit Premium and Other Intangible Assets (Changes in capitalized mortgage and commercial servicing rights) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Servicing Asset at Fair Value, Amount [Roll Forward]
Valuation allowance on commercial servicing rights	$ 230	$ 5	$ 12	$ 29
Sale of mortgage servicing rights					$ (6,900)
Mortgage Servicing Rights
Servicing Asset at Fair Value, Amount [Roll Forward]
Balance at beginning of period			23,248	32,088	32,088
Originations			4,322	5,778
Amortization			(4,394)	(7,184)
Valuation allowance on commercial servicing rights			0	0
Sale of mortgage servicing rights			0	(6,940)
Acquired mortgage servicing rights			6,995	0
Balance at end of period	30,171	23,742	30,171	23,742	23,248
Fair value of commercial servicing rights	47,581	35,002	$ 47,581	$ 35,002	37,100
Commercial servicing rights, net to servicing portfolio			0.73%	0.67%
Commercial servicing rights
Servicing Asset at Fair Value, Amount [Roll Forward]
Balance at beginning of period			$ 2,609	$ 3,690	3,690
Originations			82	215
Amortization			(835)	(1,077)
Valuation allowance on commercial servicing rights			12	29
Balance at end of period	1,868	2,857	1,868	2,857	2,609
Fair value of commercial servicing rights	$ 2,529	$ 3,458	$ 2,529	$ 3,458	$ 3,200
Commercial servicing rights, net to servicing portfolio			1.63%	1.98%