Loans Receivable, Net - Aging of Recorded Investment in Past Due Loans Excluding PCI Loans (Detail) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Financing Receivable, Past Due [Line Items]
Total Past Due	$ 32,401	$ 39,728
Greater than 90 Days Past Due	9,836	9,573
Loans Not Past Due	6,044,451	5,540,084
Total loans	6,076,852	5,579,812
30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	14,624	21,482
60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	7,941	8,673
Commercial and Industrial
Financing Receivable, Past Due [Line Items]
Total Past Due	690	0
Greater than 90 Days Past Due	207	0
Loans Not Past Due	405,280	304,994
Total loans	405,970	304,994
Commercial and Industrial | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	483	0
Commercial and Industrial | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	0	0
Commercial real estate – owner occupied
Financing Receivable, Past Due [Line Items]
Total Past Due	5,823	5,537
Greater than 90 Days Past Due	984	197
Loans Not Past Due	781,029	734,838
Total loans	786,852	740,375
Commercial real estate – owner occupied | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	2,107	5,104
Commercial real estate – owner occupied | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	2,732	236
Commercial real estate – investor
Financing Receivable, Past Due [Line Items]
Total Past Due	7,433	8,943
Greater than 90 Days Past Due	3,939	2,461
Loans Not Past Due	2,213,366	2,006,267
Total loans	2,220,799	2,015,210
Commercial real estate – investor | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	1,489	3,979
Commercial real estate – investor | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	2,005	2,503
Residential real estate
Financing Receivable, Past Due [Line Items]
Total Past Due	14,803	19,629
Greater than 90 Days Past Due	2,409	4,451
Loans Not Past Due	2,219,223	2,024,657
Total loans	2,234,026	2,044,286
Residential real estate | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	9,619	10,199
Residential real estate | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	2,775	4,979
Consumer
Financing Receivable, Past Due [Line Items]
Total Past Due	3,652	5,619
Greater than 90 Days Past Due	2,297	2,464
Loans Not Past Due	425,553	469,328
Total loans	429,205	474,947
Consumer | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	926	2,200
Consumer | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	$ 429	$ 955