Goodwill	12 Months Ended
Dec. 31, 2015
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill	GOODWILL Goodwill was $287.4 million at December 31, 2015 and $180.1 million at December 31, 2014. During 2015, the Corporation acquired Lake Michigan and Monarch, which resulted in the recognition of goodwill for each transaction of $101.6 million and $5.3 million, respectively. During 2014, the Corporation acquired Northwestern, which resulted in the recognition of $60.0 million of goodwill. The Corporation also recorded additional goodwill in 2015 of $0.3 million related to the acquisition of Northwestern resulting from adjustments to the original acquisition date valuation of acquired assets and liabilities. Goodwill recognized in the Lake Michigan, Monarch and Northwestern transactions was primarily attributable to the synergies and economies of scale expected from combining their operations with the Corporation. None of the goodwill recorded in conjunction with the Lake Michigan, Monarch and Northwestern acquisitions is deductible for tax purposes. Goodwill is subject to impairment testing annually and on an interim basis if events or changes in circumstances indicate assets might be impaired. The Corporation's most recent annual goodwill impairment assessment, which was performed as of October 31, 2015, did not indicate that an impairment of goodwill existed. The Corporation also determined that no triggering events occurred that indicated impairment from the most recent assessment date through December 31, 2015 and that the Corporation's goodwill was not impaired at December 31, 2015.

GOODWILL

Goodwill was $287.4 million at December 31, 2015 and $180.1 million at December 31, 2014. During 2015, the Corporation acquired Lake Michigan and Monarch, which resulted in the recognition of goodwill for each transaction of $101.6 million and $5.3 million, respectively. During 2014, the Corporation acquired Northwestern, which resulted in the recognition of $60.0 million of goodwill. The Corporation also recorded additional goodwill in 2015 of $0.3 million related to the acquisition of Northwestern resulting from adjustments to the original acquisition date valuation of acquired assets and liabilities. Goodwill recognized in the Lake Michigan, Monarch and Northwestern transactions was primarily attributable to the synergies and economies of scale expected from combining their operations with the Corporation. None of the goodwill recorded in conjunction with the Lake Michigan, Monarch and Northwestern acquisitions is deductible for tax purposes.

Goodwill is subject to impairment testing annually and on an interim basis if events or changes in circumstances indicate assets might be impaired. The Corporation's most recent annual goodwill impairment assessment, which was performed as of October 31, 2015, did not indicate that an impairment of goodwill existed. The Corporation also determined that no triggering events occurred that indicated impairment from the most recent assessment date through December 31, 2015 and that the Corporation's goodwill was not impaired at December 31, 2015.