Loans Receivable, Net - Aging of Recorded Investment in Past Due Loans Excluding PCI Loans (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Financing Receivable, Past Due [Line Items]
Total Past Due	$ 26,636	$ 39,728
90 Days or Greater Past Due	9,286	9,573
Loans Not Past Due	6,174,751	5,540,084
Total	6,201,387	5,579,812
30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	11,231	21,482
60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	6,119	8,673
Commercial and industrial
Financing Receivable, Past Due [Line Items]
Total Past Due	307	0
90 Days or Greater Past Due	207	0
Loans Not Past Due	395,784	304,994
Total	396,091	304,994
Commercial and industrial | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	100	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	3,784	5,537
90 Days or Greater Past Due	1,040	197
Loans Not Past Due	788,157	734,838
Total	791,941	740,375
Commercial real estate – owner occupied | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	1,541	5,104
Commercial real estate – owner occupied | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	1,203	236
Commercial real estate - investor
Financing Receivable, Past Due [Line Items]
Total Past Due	4,111	8,943
90 Days or Greater Past Due	2,792	2,461
Loans Not Past Due	2,280,587	2,006,267
Total	2,284,698	2,015,210
Commercial real estate - investor | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	381	3,979
Commercial real estate - investor | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	938	2,503
Residential real estate
Financing Receivable, Past Due [Line Items]
Total Past Due	14,507	19,629
90 Days or Greater Past Due	2,859	4,451
Loans Not Past Due	2,306,314	2,024,657
Total	2,320,821	2,044,286
Residential real estate | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	8,161	10,199
Residential real estate | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	3,487	4,979
Consumer
Financing Receivable, Past Due [Line Items]
Total Past Due	3,927	5,619
90 Days or Greater Past Due	2,388	2,464
Loans Not Past Due	403,909	469,328
Total	407,836	474,947
Consumer | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	1,048	2,200
Consumer | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	$ 491	$ 955