Goodwill, Core Deposit Premium and Other Intangible Assets (Changes in capitalized mortgage and commercial servicing rights) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Servicing Asset at Fair Value, Amount [Roll Forward]
Valuation allowance on commercial servicing rights	$ (2)	$ 5
Mortgage Servicing Rights
Servicing Asset at Fair Value, Amount [Roll Forward]
Balance at beginning of period	23,248	32,088
Originations	1,162	2,132
Amortization	(1,245)	(2,261)
Balance at end of period	23,165	31,959
Fair value of mortgage servicing rights	$ 40,434	$ 47,564	$ 37,100
Mortgage servicing rights, net to servicing portfolio (percent)	0.66%	0.74%
Commercial servicing rights
Servicing Asset at Fair Value, Amount [Roll Forward]
Balance at beginning of period	$ 2,609	$ 3,690
Originations	21	93
Amortization	(322)	(306)
Valuation allowance on commercial servicing rights	(2)	5
Balance at end of period	2,306	3,482
Fair value of mortgage servicing rights	$ 2,781	$ 4,040	$ 3,200
Mortgage servicing rights, net to servicing portfolio (percent)	1.84%	2.17%