Loans Receivable, Net - Aging of Recorded Investment in Past Due Loans Excluding PCI Loans (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	$ 38,188	$ 36,165
Greater than 90 Days Past Due	12,262	10,917
Loans Not Past Due	3,861,539	3,785,721
Total loans	3,899,727	3,821,886
30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	16,516	20,561
60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	9,410	4,687
Residential Real Estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	21,885	19,729
Greater than 90 Days Past Due	2,277	7,159
Loans Not Past Due	1,728,070	1,692,744
Total loans	1,749,955	1,712,473
Residential Real Estate | 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	12,736	9,532
Residential Real Estate | 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	6,872	3,038
Commercial Real Estate - Owner Occupied
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1,000	5,884
Greater than 90 Days Past Due	289	890
Loans Not Past Due	552,971	528,330
Total loans	553,971	534,214
Commercial Real Estate - Owner Occupied | 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	711	3,962
Commercial Real Estate - Owner Occupied | 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	1,032
Commercial Real Estate - Investor
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	10,620	521
Greater than 90 Days Past Due	8,146	521
Loans Not Past Due	1,122,498	1,131,554
Total loans	1,133,118	1,132,075
Commercial Real Estate - Investor | 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	2,301	0
Commercial Real Estate - Investor | 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	173	0
Consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	2,745	3,918
Greater than 90 Days Past Due	1,486	1,963
Loans Not Past Due	276,518	286,637
Total loans	279,263	290,555
Consumer | 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	768	1,519
Consumer | 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	491	436
Commercial and Industrial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1,938	6,113
Greater than 90 Days Past Due	64	384
Loans Not Past Due	181,482	146,456
Total loans	183,420	152,569
Commercial and Industrial | 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	5,548
Commercial and Industrial | 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	$ 1,874	$ 181