Intangible Assets (Net Carrying Value) (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015	May. 31, 2015	Mar. 31, 2015	Dec. 31, 2014
Net carrying value of intangible assets
Goodwill	$ 286,867	$ 287,393		$ 180,128
Other intangible assets:
Total other intangible assets	36,266	38,104		31,655
Core deposit intangible assets [Member]
Other intangible assets:
Finite-Lived Core Deposits, Gross	25,542	26,654		20,072
Total other intangible assets	25,542	26,654		20,072
Noncompete Agreements [Member]
Other intangible assets:
Finite-Lived Noncompete Agreements, Gross	246	328		0
Mortgage servicing rights [Member]
Other intangible assets:
Servicing Asset at Amortized Cost	10,478	11,122		11,583
Total other intangible assets	$ 10,478	$ 11,122		$ 11,583	$ 12,217
Lake Michigan Financial Corp [Member]
Net carrying value of intangible assets
Goodwill			$ 101,000