Consolidated Statements of Changes in Shareholders' Equity (USD $)	Preferred Stock [Member]	Common Stock [Member]	Common Stock Warrant [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Total
Balances at Dec. 31, 2011	$ 20,331,000	$ 172,841,000	$ 1,138,000	$ (32,639,000)	$ 3,328,000	$ 164,999,000
Repurchase of preferred stock	(21,000,000)					(21,000,000)
Preferred stock dividends				(361,000)		(361,000)
Accretion of preferred stock	669,000			(669,000)		0
Repurchase of stock warrant		(6,327,000)	(1,138,000)			(7,465,000)
Employee stock purchase plan		39,000				39,000
Dividend reinvestment plan		14,000				14,000
Stock option exercises		551,000				551,000
Stock tendered for stock option exercises		(324,000)				(324,000)
Stock-based compensation expense		54,000				54,000
Cash dividends		(774,000)				(774,000)
Net income				12,535,000		12,535,000
Change in net unrealized gain on securities available for sale, net of tax effect					(955,000)	(955,000)
Change in fair value of interest rate swap, net tax effect					(723,000)	(723,000)
Balances at Dec. 31, 2012	0	166,074,000	0	(21,134,000)	1,650,000	146,590,000
Employee stock purchase plan		19,000				19,000
Dividend reinvestment plan		33,000				33,000
Stock option exercises		700,000				700,000
Stock tendered for stock option exercises		(411,000)				(411,000)
Stock-based compensation expense		473,000				473,000
Cash dividends		(3,889,000)				(3,889,000)
Net income				17,033,000		17,033,000
Change in net unrealized gain on securities available for sale, net of tax effect					(7,774,000)	(7,774,000)
Change in fair value of interest rate swap, net tax effect					551,000	551,000
Balances at Dec. 31, 2013	0	162,999,000	0	(4,101,000)	(5,573,000)	153,325,000
Common stock issued in connection with Firstbank merger (8,087,272 shares)		173,310,000				173,310,000
Issuance of stock options to replace existing Firstbank options at merger date		1,664,000				1,664,000
Employee stock purchase plan		23,000				23,000
Dividend reinvestment plan		209,000				209,000
Stock option exercises		282,000				282,000
Stock grants to directors for retainer fees (7,375 shares)		155,000				155,000
Stock-based compensation expense		714,000				714,000
Cash dividends		(21,452,000)		(3,012,000)		(24,464,000)
Net income				17,331,000		17,331,000
Change in net unrealized gain on securities available for sale, net of tax effect					5,582,000	5,582,000
Change in fair value of interest rate swap, net tax effect					7,000	7,000
Balances at Dec. 31, 2014	$ 0	$ 317,904,000	$ 0	$ 10,218,000	$ 16,000	$ 328,138,000