Loans and Leases Receivable and Allowance for Credit Losses - Non-Covered Loans and Covered Loans by Class and Performance Status (Detail) - USD ($) $ in Thousands		3 Months Ended	6 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2020	Dec. 31, 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	$ 113,159		$ 113,159	$ 35,123
Non-accrual	67,341		67,341	20,021
Loans and leases not past due	7,159,288		7,159,288	7,244,271
Purchased-credit-impaired loans	15,700	$ 17,488
Loans and lease receivable, gross	7,272,447		$ 7,272,447	7,318,988
Financing receivable, at amortized cost or lower of cost or market				7,316,903
Delinquent period			30 days
Loans receivable, PPP	4,760,427		$ 4,760,427	0
30 to 59 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	21,838		21,838
60 to 89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	22,242		22,242
30-89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due				33,329
90 Days or More Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	69,079		69,079	1,794
Multi-family
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	23,803		23,803	2,133
Non-accrual	7,013		7,013	4,117
Loans and leases not past due	1,558,036		1,558,036	1,901,336
Purchased-credit-impaired loans		1,688
Loans and lease receivable, gross	1,581,839		1,581,839	1,909,274
Multi-family | 30 to 59 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	0		0
Multi-family | 60 to 89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	16,790		16,790
Multi-family | 30-89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due				2,133
Multi-family | 90 Days or More Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	7,013		7,013	0
Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	10,620		10,620	2,395
Non-accrual	9,974		9,974	4,531
Loans and leases not past due	2,088,822		2,088,822	1,882,700
Purchased-credit-impaired loans		354
Loans and lease receivable, gross	2,099,442		2,099,442	1,889,980
Commercial and industrial | 30 to 59 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	523		523
Commercial and industrial | 60 to 89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	123		123
Commercial and industrial | 30-89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due				2,395
Commercial and industrial | 90 Days or More Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	9,974		9,974	0
Commercial real estate owner occupied
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	8,910		8,910	5,388
Non-accrual	4,022		4,022	1,963
Loans and leases not past due	535,862		535,862	537,992
Purchased-credit-impaired loans		6,664
Loans and lease receivable, gross	544,772		544,772	552,007
Commercial real estate owner occupied | 30 to 59 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	0		0
Commercial real estate owner occupied | 60 to 89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	4,888		4,888
Commercial real estate owner occupied | 30-89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due				5,388
Commercial real estate owner occupied | 90 Days or More Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	4,022		4,022	0
Commercial real estate non-owner occupied
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	30,354		30,354	8,034
Non-accrual	30,257		30,257	76
Loans and leases not past due	1,214,419		1,214,419	1,211,892
Purchased-credit-impaired loans		3,527
Loans and lease receivable, gross	1,244,773		1,244,773	1,223,529
Commercial real estate non-owner occupied | 30 to 59 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	97		97
Commercial real estate non-owner occupied | 60 to 89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	0		0
Commercial real estate non-owner occupied | 30-89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due				8,034
Commercial real estate non-owner occupied | 90 Days or More Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	30,257		30,257	0
Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	0		0	0
Non-accrual	0		0	0
Loans and leases not past due	128,834		128,834	118,418
Purchased-credit-impaired loans		0
Loans and lease receivable, gross	128,834		128,834	118,418
Construction | 30 to 59 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	0		0
Construction | 60 to 89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	0		0
Construction | 30-89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due				0
Construction | 90 Days or More Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	0		0	0
Residential real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	16,929		16,929	5,924
Non-accrual	7,857		7,857	6,128
Loans and leases not past due	331,180		331,180	359,491
Purchased-credit-impaired loans		3,471
Loans and lease receivable, gross	348,109		348,109	375,014
Residential real estate | 30 to 59 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	8,631		8,631
Residential real estate | 60 to 89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	441		441
Residential real estate | 30-89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due				5,924
Residential real estate | 90 Days or More Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	7,857		7,857	0
Manufactured housing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	6,241		6,241	5,493
Non-accrual	3,331		3,331	1,655
Loans and leases not past due	60,624		60,624	61,649
Purchased-credit-impaired loans		1,601
Loans and lease receivable, gross	66,865		66,865	70,398
Manufactured housing | 30 to 59 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	1,172		1,172
Manufactured housing | 60 to 89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	0		0
Manufactured housing | 30-89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due				3,699
Manufactured housing | 90 Days or More Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	5,069		5,069	1,794
Other consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	16,302		16,302	5,756
Non-accrual	4,887		4,887	1,551
Loans and leases not past due	1,241,511		1,241,511	1,170,793
Purchased-credit-impaired loans		$ 183
Loans and lease receivable, gross	1,257,813		1,257,813	1,178,283
Other consumer | 30 to 59 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	11,415		11,415
Other consumer | 60 to 89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	0		0
Other consumer | 30-89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due				5,756
Other consumer | 90 Days or More Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	$ 4,887		$ 4,887	$ 0