Loans and Leases Receivable and Allowance for Loan and Lease Losses - Schedule of Allowance for Loan Losses (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2019	Dec. 31, 2018
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	$ 39,972	$ 38,015
Charge-offs	(9,590)	(4,757)
Recoveries	1,770	1,072
Provision for loan and lease losses	24,227	5,642
Ending Balance	56,379	39,972
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Individually evaluated for impairment			$ 31,272	$ 39,118
Collectively evaluated for impairment			7,268,143	7,077,806
Loans receivable, at amortized cost or lower of cost or market			7,316,903	7,138,498
Individually evaluated for impairment			852	845
Collectively evaluated for impairment			52,901	36,249
Total allowance for loan losses	39,972	39,972	56,379	39,972
Purchased credit impaired loans
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Loans acquired with credit deterioration			17,488	21,574
Loans receivable, at amortized cost or lower of cost or market			17,488	21,574
Loans acquired with credit deterioration			2,626	2,878
Multi-family
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	11,462	12,168
Charge-offs	(541)	0
Recoveries	7	0
Provision for loan and lease losses	(4,771)	(706)
Ending Balance	6,157	11,462
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Individually evaluated for impairment			4,117	1,155
Collectively evaluated for impairment			1,903,469	3,282,452
Loans receivable, at amortized cost or lower of cost or market			1,909,274	3,285,297
Individually evaluated for impairment			0	539
Collectively evaluated for impairment			6,157	10,923
Total allowance for loan losses	11,462	11,462	6,157	11,462
Multi-family | Purchased credit impaired loans
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Loans acquired with credit deterioration			1,688	1,690
Loans receivable, at amortized cost or lower of cost or market			1,688	1,690
Loans acquired with credit deterioration			0	0
Commercial and industrial
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	12,145	10,918
Charge-offs	(532)	(1,722)
Recoveries	1,050	403
Provision for loan and lease losses	2,893	2,546
Ending Balance	15,556	12,145
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Individually evaluated for impairment			4,591	17,828
Collectively evaluated for impairment			1,885,035	1,355,436
Loans receivable, at amortized cost or lower of cost or market			1,889,980	1,373,800
Individually evaluated for impairment			523	261
Collectively evaluated for impairment			14,768	11,516
Total allowance for loan losses	12,145	12,145	15,556	12,145
Commercial and industrial | Purchased credit impaired loans
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Loans acquired with credit deterioration			354	536
Loans receivable, at amortized cost or lower of cost or market			354	536
Loans acquired with credit deterioration			265	368
Commercial real estate owner occupied
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	3,320	3,232
Charge-offs	(119)	(747)
Recoveries	236	326
Provision for loan and lease losses	(1,202)	509
Ending Balance	2,235	3,320
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Individually evaluated for impairment			1,976	1,069
Collectively evaluated for impairment			543,367	567,970
Loans receivable, at amortized cost or lower of cost or market			552,007	577,477
Individually evaluated for impairment			83	1
Collectively evaluated for impairment			2,113	3,319
Total allowance for loan losses	3,320	3,320	2,235	3,320
Commercial real estate owner occupied | Purchased credit impaired loans
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Loans acquired with credit deterioration			6,664	8,438
Loans receivable, at amortized cost or lower of cost or market			6,664	8,438
Loans acquired with credit deterioration			39	0
Commercial real estate non-owner occupied
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	6,093	7,437
Charge-offs	0	0
Recoveries	0	5
Provision for loan and lease losses	150	(1,349)
Ending Balance	6,243	6,093
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Individually evaluated for impairment			76	129
Collectively evaluated for impairment			1,219,926	1,120,633
Loans receivable, at amortized cost or lower of cost or market			1,223,529	1,125,106
Individually evaluated for impairment			0	0
Collectively evaluated for impairment			4,361	4,161
Total allowance for loan losses	6,093	6,093	6,243	6,093
Commercial real estate non-owner occupied | Purchased credit impaired loans
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Loans acquired with credit deterioration			3,527	4,344
Loans receivable, at amortized cost or lower of cost or market			3,527	4,344
Loans acquired with credit deterioration			1,882	1,932
Construction
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	624	979
Charge-offs	0	0
Recoveries	136	241
Provision for loan and lease losses	502	(596)
Ending Balance	1,262	624
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Individually evaluated for impairment			0	0
Collectively evaluated for impairment			118,418	56,491
Loans receivable, at amortized cost or lower of cost or market			118,418	56,491
Individually evaluated for impairment			0	0
Collectively evaluated for impairment			1,262	624
Total allowance for loan losses	1,262	979	1,262	624
Construction | Purchased credit impaired loans
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Loans acquired with credit deterioration			0	0
Loans receivable, at amortized cost or lower of cost or market			0	0
Loans acquired with credit deterioration			0	0
Residential real estate
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	3,654	2,929
Charge-offs	(297)	(466)
Recoveries	27	76
Provision for loan and lease losses	(166)	1,115
Ending Balance	3,218	3,654
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Individually evaluated for impairment			9,063	8,631
Collectively evaluated for impairment			362,480	553,593
Loans receivable, at amortized cost or lower of cost or market			375,014	566,561
Individually evaluated for impairment			44	41
Collectively evaluated for impairment			2,923	3,227
Total allowance for loan losses	3,654	3,654	3,218	3,654
Residential real estate | Purchased credit impaired loans
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Loans acquired with credit deterioration			3,471	4,337
Loans receivable, at amortized cost or lower of cost or market			3,471	4,337
Loans acquired with credit deterioration			251	386
Manufactured housing
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	145	180
Charge-offs	0	0
Recoveries	0	0
Provision for loan and lease losses	915	(35)
Ending Balance	1,060	145
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Individually evaluated for impairment			9,898	10,195
Collectively evaluated for impairment			58,899	67,528
Loans receivable, at amortized cost or lower of cost or market			70,398	79,731
Individually evaluated for impairment			129	3
Collectively evaluated for impairment			897	89
Total allowance for loan losses	145	145	1,060	145
Manufactured housing | Purchased credit impaired loans
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Loans acquired with credit deterioration			1,601	2,008
Loans receivable, at amortized cost or lower of cost or market			1,601	2,008
Loans acquired with credit deterioration			34	53
Other consumer
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	2,529	172
Charge-offs	(8,101)	(1,822)
Recoveries	314	21
Provision for loan and lease losses	25,906	4,158
Ending Balance	20,648	2,529
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Individually evaluated for impairment			1,551	111
Collectively evaluated for impairment			1,176,549	73,703
Loans receivable, at amortized cost or lower of cost or market			1,178,283	74,035
Individually evaluated for impairment			73	0
Collectively evaluated for impairment			20,420	2,390
Total allowance for loan losses	$ 20,648	$ 172	20,648	2,529
Other consumer | Purchased credit impaired loans
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Loans acquired with credit deterioration			183	221
Loans receivable, at amortized cost or lower of cost or market			183	221
Loans acquired with credit deterioration			$ 155	$ 139