Loans Receivable, Net - Risk Category of Loans by Loan Portfolio Segment Excluding PCI Loans (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Financing Receivable, Recorded Investment [Line Items]
Loan	$ 3,060,579	$ 1,943,444
Commercial and industrial
Financing Receivable, Recorded Investment [Line Items]
Loan	304,994	187,645
Commercial real estate - owner occupied
Financing Receivable, Recorded Investment [Line Items]
Loan	740,375	569,497
Commercial real estate – investor
Financing Receivable, Recorded Investment [Line Items]
Loan	2,015,210	1,186,302
Pass
Financing Receivable, Recorded Investment [Line Items]
Loan	2,964,585	1,874,637
Pass | Commercial and industrial
Financing Receivable, Recorded Investment [Line Items]
Loan	291,265	181,438
Pass | Commercial real estate - owner occupied
Financing Receivable, Recorded Investment [Line Items]
Loan	706,825	546,569
Pass | Commercial real estate – investor
Financing Receivable, Recorded Investment [Line Items]
Loan	1,966,495	1,146,630
Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loan	29,504	22,134
Special Mention | Commercial and industrial
Financing Receivable, Recorded Investment [Line Items]
Loan	2,777	3,153
Special Mention | Commercial real estate - owner occupied
Financing Receivable, Recorded Investment [Line Items]
Loan	3,000	4,337
Special Mention | Commercial real estate – investor
Financing Receivable, Recorded Investment [Line Items]
Loan	23,727	14,644
Substandard
Financing Receivable, Recorded Investment [Line Items]
Loan	66,490	46,673
Substandard | Commercial and industrial
Financing Receivable, Recorded Investment [Line Items]
Loan	10,952	3,054
Substandard | Commercial real estate - owner occupied
Financing Receivable, Recorded Investment [Line Items]
Loan	30,550	18,591
Substandard | Commercial real estate – investor
Financing Receivable, Recorded Investment [Line Items]
Loan	24,988	25,028
Doubtful
Financing Receivable, Recorded Investment [Line Items]
Loan	0	0
Doubtful | Commercial and industrial
Financing Receivable, Recorded Investment [Line Items]
Loan	0	0
Doubtful | Commercial real estate - owner occupied
Financing Receivable, Recorded Investment [Line Items]
Loan	0	0
Doubtful | Commercial real estate – investor
Financing Receivable, Recorded Investment [Line Items]
Loan	$ 0	$ 0