Intangible Assets (Net Carrying Value) (Details) - USD ($) $ in Thousands	Jun. 30, 2015	May. 31, 2015	Mar. 31, 2015	Dec. 31, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013
Net carrying value of intangible assets
Goodwill	$ 285,512			$ 180,128	$ 120,164
Other intangible assets:
Total other intangible assets	41,201			33,080	12,454
Core deposit intangible assets [Member]
Other intangible assets:
Finite-Lived Core Deposits, Gross	28,353			20,863	9,110
Total other intangible assets	28,353			20,863	9,110
Noncompete Agreements [Member]
Other intangible assets:
Finite-Lived Noncompete Agreements, Gross					0			$ 0
Mortgage servicing rights [Member]
Other intangible assets:
Servicing Asset at Amortized Cost	12,307			12,217	3,344
Total other intangible assets	12,307		$ 11,583	$ 12,217	$ 3,344	$ 3,316	$ 3,423
Lake Michigan Financial Corp [Member]
Net carrying value of intangible assets
Goodwill		$ 100,002
Other intangible assets:
Finite-Lived Noncompete Agreements, Gross	$ 541	$ 600