Loans Receivable, Net - Allowance for Loan Loses and Recorded Investment in Loans by Portfolio Segment and Based on Impairment Method Excluding PCI Loans (Detail) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of year	$ 15,721	$ 15,183	$ 16,722
Provision (benefit) charged to operations	3,490	4,445
Charge-offs	(3,841)	(5,384)	(4,490)
Recoveries	1,207	1,477	328
Balance at end of year	16,577	15,721	15,183
Loans:
Loans individually evaluated for impairment	29,797	46,988
Loans collectively evaluated for impairment	5,550,015	3,927,414
Total loans	5,579,812	3,974,402
Ending allowance balance attributed to loans:
Individually evaluated for impairment	0	0
Collectively evaluated for impairment	16,577	15,721
Total ending allowance balance	16,577	15,721
Commercial and industrial
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of year	1,801	2,037
Provision (benefit) charged to operations	(66)	(379)
Charge-offs	(230)	(380)
Recoveries	104	523
Balance at end of year	1,609	1,801	2,037
Loans:
Loans individually evaluated for impairment	1,626	864
Loans collectively evaluated for impairment	303,368	186,781
Total loans	304,994	187,645
Ending allowance balance attributed to loans:
Individually evaluated for impairment	0	0
Collectively evaluated for impairment	1,609	1,801
Total ending allowance balance	1,609	1,801
Commercial real estate - owner occupied
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of year	3,175	2,999
Provision (benefit) charged to operations	(783)	203
Charge-offs	(314)	(150)
Recoveries	199	123
Balance at end of year	2,277	3,175	2,999
Loans:
Loans individually evaluated for impairment	5,395	15,132
Loans collectively evaluated for impairment	734,980	554,365
Total loans	740,375	569,497
Ending allowance balance attributed to loans:
Individually evaluated for impairment	0	0
Collectively evaluated for impairment	2,277	3,175
Total ending allowance balance	2,277	3,175
Commercial real estate – investor
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of year	7,952	6,361
Provision (benefit) charged to operations	2,550	2,444
Charge-offs	(1,939)	(899)
Recoveries	207	46
Balance at end of year	8,770	7,952	6,361
Loans:
Loans individually evaluated for impairment	9,738	17,923
Loans collectively evaluated for impairment	2,005,472	1,168,379
Total loans	2,015,210	1,186,302
Ending allowance balance attributed to loans:
Individually evaluated for impairment	0	0
Collectively evaluated for impairment	8,770	7,952
Total ending allowance balance	8,770	7,952
Residential mortgage
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of year	1,804	2,245
Provision (benefit) charged to operations	1,056	2,742
Charge-offs	(1,021)	(3,820)
Recoveries	574	637
Balance at end of year	2,413	1,804	2,245
Loans:
Loans individually evaluated for impairment	10,064	10,605
Loans collectively evaluated for impairment	2,034,222	1,737,985
Total loans	2,044,286	1,748,590
Ending allowance balance attributed to loans:
Individually evaluated for impairment	0	0
Collectively evaluated for impairment	2,413	1,804
Total ending allowance balance	2,413	1,804
Consumer
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of year	614	1,110
Provision (benefit) charged to operations	86	(509)
Charge-offs	(337)	(135)
Recoveries	123	148
Balance at end of year	486	614	1,110
Loans:
Loans individually evaluated for impairment	2,974	2,464
Loans collectively evaluated for impairment	471,973	279,904
Total loans	474,947	282,368
Ending allowance balance attributed to loans:
Individually evaluated for impairment	0	0
Collectively evaluated for impairment	486	614
Total ending allowance balance	486	614
Unallocated
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of year	375	431
Provision (benefit) charged to operations	647	(56)
Charge-offs	0	0
Recoveries	0	0
Balance at end of year	1,022	375	$ 431
Loans:
Loans individually evaluated for impairment	0	0
Loans collectively evaluated for impairment	0	0
Total loans	0	0
Ending allowance balance attributed to loans:
Individually evaluated for impairment	0	0
Collectively evaluated for impairment	1,022	375
Total ending allowance balance	$ 1,022	$ 375

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Provision Benefit for Loan and Lease Losses

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Amount of recovery of loans and lease receivables which had previously been fully or partially written-off as bad debts.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Amount of loans and leases that have been written off from both loan receivables and allowance reserve for credit loss.

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A valuation allowance for financing receivables that are expected to be uncollectible.

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Amount of valuation allowance for financing receivables that are expected to be uncollectible that were individually evaluated for impairment.

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Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

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Amount before allowance of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements.

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