Commitments, Contingencies and Concentrations of Credit Risk - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Other Commitments [Line Items]
Fixed-rate loan commitments	90 days
Rental expense	$ 1,984,000	$ 2,378,000	$ 2,034,000
Interest payments period	7 years
Accrual Status [Member]
Other Commitments [Line Items]
Amount of interest-only one-to-four family mortgage loans	17,600,000	28,800,000
Amount of stated income loans	27,300,000	36,600,000
Non-Accrual Status [Member]
Other Commitments [Line Items]
Amount of interest-only non-accrual one-to-four family mortgage loans	0	2,200,000
Amount of stated income non-accrual loans	$ 259,000	$ 6,400,000
Minimum [Member]
Other Commitments [Line Items]
Interest rates	3.00%
Interest payments period	5 years
Maximum [Member]
Other Commitments [Line Items]
Interest rates	5.49%
Interest payments period	10 years