Mergers and Acquisitions - Textual (Details) $ / shares in Units, shares in Millions		3 Months Ended		9 Months Ended
	Aug. 31, 2016 USD ($) $ / shares shares	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)
Business Acquisition
Business Acquisition, Pro Forma Revenue				$ 0
Repayments of lines of credit	$ 25,000,000
Merger expenses		$ 2,379,000	$ 37,470,000	7,011,000	$ 43,118,000
Talmer
Business Acquisition
Business Acquisition, Pro Forma Revenue		175,750,000	$ 175,783,000	$ 523,373,000	$ 503,501,000
Acquisition purchase price	$ 1,612,449,000
Stock consideration given (in shares) | shares	32.1
Exchange ratio of common stock issued	0.4725
Share price (dollars per share) | $ / shares	$ 1.61
Credit facility used for acquisition	$ 125,000,000
Repayments of lines of credit	$ 37,500,000
Increase in goodwill		$ 1,000,000