Intangible Assets (Net Carrying Value) (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Jun. 30, 2015	May 31, 2015	Mar. 31, 2015	Dec. 31, 2014
Net carrying value of intangible assets
Goodwill	$ 286,867		$ 287,393	$ 285,512
Other intangible assets:
Total other intangible assets	34,270		38,104	41,201
Core deposit intangible assets [Member]
Other intangible assets:
Finite-Lived Core Deposits, Gross	24,429		26,654	28,353
Total other intangible assets	24,429		26,654	28,353
Noncompete Agreements [Member]
Other intangible assets:
Finite-Lived Noncompete Agreements, Gross	164		328	541
Mortgage Servicing Rights [Member]
Other intangible assets:
Servicing Asset at Amortized Cost	9,677		11,122	12,307
Total other intangible assets	$ 9,677	$ 10,478	$ 11,122	$ 12,307		$ 11,583	$ 12,217
Lake Michigan Financial Corp [Member]
Net carrying value of intangible assets
Goodwill					$ 101,000