Intangible Assets (Net Carrying Value) (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Jun. 30, 2015	May. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013
Net carrying value of intangible assets
Goodwill	$ 286,454			$ 180,128	$ 120,164
Other intangible assets:
Total other intangible assets	39,864			33,080	11,958
Core deposit intangible assets [Member]
Other intangible assets:
Finite-Lived Core Deposits, Gross	27,890			20,863	8,665
Total other intangible assets	27,890			20,863	8,665
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	11,540			12,217	3,293
Total other intangible assets	11,540	$ 12,307		$ 12,217	$ 3,293	$ 3,344		$ 3,423
Lake Michigan Financial Corp [Member]
Net carrying value of intangible assets
Goodwill			$ 100,878
Other intangible assets:
Finite-Lived Noncompete Agreements, Gross	$ 434		$ 600