Condensed Consolidated Statements of Changes in Shareholders' Equity [Unaudited] - USD ($)	Preferred Stock [Member]	Common Stock [Member]	Retained Earnings [Member]	AOCI Attributable to Parent [Member]	Total
Balances, at Dec. 31, 2013	$ 0	$ 162,999,000	$ (4,101,000)	$ (5,573,000)	$ 153,325,000
Employee stock purchase plan		10,000			10,000
Dividend reinvestment plan		90,000			90,000
Stock option exercises		229,000			229,000
Stock grants to directors for retainer fees		155,000			155,000
Stock-based compensation expense		364,000			364,000
Cash dividends		(21,447,000)	(989,000)		(22,436,000)
Common stock issued in connection with Firstbank merger (8,087,272 shares)		173,310,000			173,310,000
Stock options issued to replace existing Firstbank options at merger date		1,664,000			1,664,000
Net income			11,038,000		11,038,000
Change in net unrealized gain on securities available for sale, net of tax effect				3,160,000	3,160,000
Change in fair value of interest rate swap, net of tax effect				84,000	84,000
Balances, at Sep. 30, 2014	0	317,374,000	5,948,000	(2,329,000)	320,993,000
Balances, at Dec. 31, 2014	0	317,904,000	10,218,000	16,000	328,138,000
Employee stock purchase plan		33,000			33,000
Dividend reinvestment plan		456,000			456,000
Stock option exercises		281,000			281,000
Stock grants to directors for retainer fees		402,000			402,000
Stock-based compensation expense		525,000			525,000
Share repurchase program (765,260 shares)		(15,223,000)			(15,223,000)
Cash dividends			(7,085,000)		(7,085,000)
Net income			20,540,000		20,540,000
Change in net unrealized gain on securities available for sale, net of tax effect				934,000	934,000
Change in fair value of interest rate swap, net of tax effect				(181,000)	(181,000)
Balances, at Sep. 30, 2015	$ 0	$ 304,378,000	$ 23,673,000	$ 769,000	$ 328,820,000