Mergers and Acquisitions - Pro Forma Information (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Business Acquisition
Provision for Loan and Lease Losses	$ 5,499,000	$ 4,103,000	$ 15,778,000	$ 8,603,000
Net interest and other income			0
Talmer Bank
Business Acquisition
Net interest and other income	175,750,000	175,783,000	523,373,000	503,501,000
Net Income	$ 40,459,000	$ 10,439,000	$ 140,077,000	$ 86,911,000
Earnings per share:
Basic (dollars per share)	$ 0.57	$ 0.15	$ 1.98	$ 1.23
Diluted (dollars per share)	$ 0.56	$ 0.15	$ 1.95	$ 1.22