Loans Receivable, Net - Risk Category of Loans by Loan Portfolio Segment Excluding PCI Loans (Detail) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	$ 3,413,621	$ 3,060,579
Commercial and Industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	405,970	304,994
Commercial real estate – owner occupied
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	786,852	740,375
Commercial real estate – investor
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	2,220,799	2,015,210
Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	3,304,606	2,964,585
Pass | Commercial and Industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	391,823	291,265
Pass | Commercial real estate – owner occupied
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	759,858	706,825
Pass | Commercial real estate – investor
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	2,152,925	1,966,495
Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	57,780	29,504
Special Mention | Commercial and Industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	1,785	2,777
Special Mention | Commercial real estate – owner occupied
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	3,590	3,000
Special Mention | Commercial real estate – investor
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	52,405	23,727
Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	51,235	66,490
Substandard | Commercial and Industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	12,362	10,952
Substandard | Commercial real estate – owner occupied
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	23,404	30,550
Substandard | Commercial real estate – investor
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	15,469	24,988
Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	0	0
Doubtful | Commercial and Industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	0	0
Doubtful | Commercial real estate – owner occupied
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	0	0
Doubtful | Commercial real estate – investor
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	$ 0	$ 0