Loans Receivable, Net - Aging of Recorded Investment in Past Due Loans Excluding PCI Loans (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	$ 39,728	$ 36,909
Greater than 90 Days Past Due	9,573	15,471
Loans Not Past Due	5,540,084	3,937,493
Total loans	5,579,812	3,974,402
30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	21,482	17,315
60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	8,673	4,123
Commercial and industrial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	3,233
Greater than 90 Days Past Due	0	503
Loans Not Past Due	304,994	184,412
Total loans	304,994	187,645
Commercial and industrial | 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	2,694
Commercial and industrial | 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	36
Commercial real estate - owner occupied
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	5,537	5,624
Greater than 90 Days Past Due	197	5,402
Loans Not Past Due	734,838	563,873
Total loans	740,375	569,497
Commercial real estate - owner occupied | 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	5,104	222
Commercial real estate - owner occupied | 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	236	0
Commercial real estate – investor
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	8,943	6,068
Greater than 90 Days Past Due	2,461	4,507
Loans Not Past Due	2,006,267	1,180,234
Total loans	2,015,210	1,186,302
Commercial real estate – investor | 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	3,979	135
Commercial real estate – investor | 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	2,503	1,426
Residential mortgage
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	19,629	18,920
Greater than 90 Days Past Due	4,451	3,372
Loans Not Past Due	2,024,657	1,729,670
Total loans	2,044,286	1,748,590
Residential mortgage | 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	10,199	13,197
Residential mortgage | 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	4,979	2,351
Consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	5,619	3,064
Greater than 90 Days Past Due	2,464	1,687
Loans Not Past Due	469,328	279,304
Total loans	474,947	282,368
Consumer | 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	2,200	1,067
Consumer | 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	$ 955	$ 310