Fair Values - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities/Fair Value	$ 123,793,000	$ 138,314,000
U.S. Government agency debt obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities/Fair Value	89,294,000	79,098,000
Mortgage-backed securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities/Fair Value	14,511,000	21,996,000
Michigan Strategic Fund bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities/Fair Value	0	11,255,000
Municipal general obligation bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities/Fair Value	17,706,000	22,743,000
Mutual funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities/Fair Value	1,365,000	1,405,000
Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets and liabilities measured at fair value on recurring basis	123,399,000	137,201,000
Fair Value, Measurements, Recurring [Member] | U.S. Government agency debt obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities/Fair Value	89,294,000	79,098,000
Fair Value, Measurements, Recurring [Member] | Mortgage-backed securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities/Fair Value	14,511,000	21,996,000
Fair Value, Measurements, Recurring [Member] | Michigan Strategic Fund bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities/Fair Value		11,255,000
Fair Value, Measurements, Recurring [Member] | Municipal general obligation bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities/Fair Value	17,706,000	22,743,000
Fair Value, Measurements, Recurring [Member] | Municipal revenue bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities/Fair Value	917,000	1,817,000
Fair Value, Measurements, Recurring [Member] | Mutual funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities/Fair Value	1,365,000	1,405,000
Fair Value, Measurements, Recurring [Member] | Interest rate swap agreement [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives	(394,000)	(1,113,000)
Fair Value, Measurements, Recurring [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets and liabilities measured at fair value on recurring basis	0	0
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | U.S. Government agency debt obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities/Fair Value	0	0
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Mortgage-backed securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities/Fair Value	0	0
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Michigan Strategic Fund bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities/Fair Value		0
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Municipal general obligation bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities/Fair Value	0	0
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Municipal revenue bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities/Fair Value	0	0
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Mutual funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities/Fair Value	0	0
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Interest rate swap agreement [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives	0	0
Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets and liabilities measured at fair value on recurring basis	123,399,000	137,201,000
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | U.S. Government agency debt obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities/Fair Value	89,294,000	79,098,000
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Mortgage-backed securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities/Fair Value	14,511,000	21,996,000
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Michigan Strategic Fund bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities/Fair Value		11,255,000
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Municipal general obligation bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities/Fair Value	17,706,000	22,743,000
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Municipal revenue bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities/Fair Value	917,000	1,817,000
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Mutual funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities/Fair Value	1,365,000	1,405,000
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Interest rate swap agreement [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives	(394,000)	(1,113,000)
Fair Value, Measurements, Recurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets and liabilities measured at fair value on recurring basis	0	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | U.S. Government agency debt obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities/Fair Value	0	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Mortgage-backed securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities/Fair Value	0	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Michigan Strategic Fund bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities/Fair Value		0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Municipal general obligation bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities/Fair Value	0	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Municipal revenue bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities/Fair Value	0	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Mutual funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities/Fair Value	0	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Interest rate swap agreement [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives	$ 0	$ 0