Securities - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Schedule of Available-for-sale Securities [Line Items]
Number of mutual funds with unrealized losses	1
Fair value of debt securities with unrealized losses	$ 88,446,000	$ 33,555,000
Aggregate depreciation of securities with unrealized losses	10,100,000	388,000
Available for sale securities/Fair Value	131,178,000	138,314,000
Total securities of specific issuer, other than U.S. Government and its agencies, maximum percentage of stockholders' equity	10.00%
Debt securities[Member]
Schedule of Available-for-sale Securities [Line Items]
Number of debt securities with unrealized losses	65
Michigan Strategic Fund bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair value of debt securities with unrealized losses	0	0
Aggregate depreciation of securities with unrealized losses	0	0
Securities available for sale	10,300,000	0	0
Available for sale securities/Fair Value	0	11,255,000
State of Michigan and all its political subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost of securities	17,400,000	23,400,000
Available for sale securities/Fair Value	17,800,000	24,600,000
U.S. Government agency debt obligations and mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Carrying value of securities pledged to secure repurchase agreements	$ 94,400,000	$ 83,800,000