Acquisition Activities - (Summary of Net Assets Acquired) (Details) - USD ($) $ in Thousands		12 Months Ended
	Aug. 01, 2015	Dec. 31, 2015	Dec. 31, 2014
Liabilities:
Non-interest bearing demand deposits		$ 815,054	$ 732,580
Interest bearing demand deposits		436,745	386,121
Savings and money market		1,394,995	1,290,436
Time deposits		1,193,883	$ 1,357,051
Consideration:
Gain on bargain purchase		$ 1,048
Pine River Bank Corporation [Member]
Assets:
Cash and due from banks	$ 32,314
Investment secruities available-for-sale (at fair value)	30,093
Non-marketable securities	2,032
Loans, net	64,279
Other real estate owned	1,488
Premises and equipment, net	3,164
Core deposit intangible asset	948
Other assets	7,749
Total assets aquired	142,067
Liabilities:
Non-interest bearing demand deposits	41,432
Interest bearing demand deposits	19,632
Savings and money market	35,460
Time deposits	33,619
Total deposits	130,143
Other liabilities	1,394
Total liabilities assumed	131,537
Identifiable net assets acquired	10,530
Consideration:
Cash	9,482
Gain on bargain purchase	$ 1,048