Loans Receivable, Net - Summary of Loans Individually Evaluated for Impairment by Loan Portfolio Segment Excluding PCI Loans (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Financing Receivable, Impaired [Line Items]
Recorded Investment	$ 45,573,000		$ 45,573,000		$ 36,979,000
Allowance for Loan Losses Allocated	2,400,000		2,400,000		2,161,000
With No Related Allowance Recorded [Member]
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance	34,935,000		34,935,000		27,482,000
Recorded Investment	34,015,000		34,015,000		26,487,000
Average Recorded Investment	33,480,000	$ 30,555,000	30,254,000	$ 30,696,000
Interest Income Recognized	256,000	255,000	799,000	700,000
With an Allowance Recorded [Member]
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance	11,626,000		11,626,000		10,492,000
Recorded Investment	11,558,000		11,558,000		10,492,000
Allowance for Loan Losses Allocated	2,400,000		2,400,000		2,161,000
Average Recorded Investment	11,527,000	11,194,000	10,746,000	11,466,000
Interest Income Recognized	2,000	48,000	22,000	152,000
Residential Real Estate [Member] | With No Related Allowance Recorded [Member]
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance	12,536,000		12,536,000		12,351,000
Recorded Investment	12,117,000		12,117,000		11,931,000
Average Recorded Investment	12,580,000	17,328,000	12,634,000	17,493,000
Interest Income Recognized	141,000	159,000	434,000	476,000
Residential Real Estate [Member] | With an Allowance Recorded [Member]
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance	294,000		294,000		948,000
Recorded Investment	260,000		260,000		948,000
Allowance for Loan Losses Allocated	67,000		67,000		88,000
Average Recorded Investment	260,000	1,462,000	261,000	1,330,000
Interest Income Recognized	2,000	13,000	8,000	44,000
Commercial Real Estate [Member] | With No Related Allowance Recorded [Member]
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance	19,095,000		19,095,000		12,174,000
Recorded Investment	18,992,000		18,992,000		12,142,000
Average Recorded Investment	17,931,000	11,186,000	14,691,000	10,883,000
Interest Income Recognized	84,000	69,000	270,000	152,000
Commercial Real Estate [Member] | With an Allowance Recorded [Member]
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance	10,578,000		10,578,000		9,023,000
Recorded Investment	10,581,000		10,581,000		9,023,000
Allowance for Loan Losses Allocated	1,991,000		1,991,000		1,741,000
Average Recorded Investment	10,635,000	9,140,000	10,153,000	9,502,000
Interest Income Recognized		25,000	11,000	77,000
Consumer [Member] | With No Related Allowance Recorded [Member]
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance	2,601,000		2,601,000		2,243,000
Recorded Investment	2,203,000		2,203,000		1,700,000
Average Recorded Investment	2,266,000	1,765,000	2,222,000	2,043,000
Interest Income Recognized	28,000	24,000	87,000	65,000
Consumer [Member] | With an Allowance Recorded [Member]
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance	207,000		207,000		521,000
Recorded Investment	170,000		170,000		521,000
Allowance for Loan Losses Allocated	22,000		22,000		332,000
Average Recorded Investment	85,000	592,000	28,000	634,000
Interest Income Recognized		10,000	1,000	31,000
Commercial and Industrial [Member] | With No Related Allowance Recorded [Member]
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance	703,000		703,000		714,000
Recorded Investment	703,000		703,000		$ 714,000
Average Recorded Investment	703,000	276,000	707,000	277,000
Interest Income Recognized	3,000	$ 3,000	8,000	$ 7,000
Commercial and Industrial [Member] | With an Allowance Recorded [Member]
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance	547,000		547,000
Recorded Investment	547,000		547,000
Allowance for Loan Losses Allocated	320,000		320,000
Average Recorded Investment	$ 547,000		304,000
Interest Income Recognized			$ 2,000