Allowance for Credit Losses - Allocation of Allowance for Loan and Lease Losses (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Allocation of allowance as well as the activity in allowance
Beginning ACL Balance	$ 266,999	$ 115,422	$ 268,018	$ 35,698
Initial ACL Recorded for PCD Loans		21,242		21,242
Charge-offs	(3,290)	(4,685)	(5,242)	(6,121)
Recoveries	2,196	35	2,814	127
Provision for Credit Losses	(33,131)	150,257	(32,816)	175,639
Ending ACL Balance	232,774	282,271	232,774	282,271
Investor loans secured by real estate | CRE non-owner-occupied
Allocation of allowance as well as the activity in allowance
Beginning ACL Balance	45,545	15,896	49,176	1,899
Initial ACL Recorded for PCD Loans		3,025		3,025
Charge-offs	0	0	(154)	(387)
Recoveries	0	0	0	0
Provision for Credit Losses	1,567	44,086	(1,910)	50,047
Ending ACL Balance	47,112	63,007	47,112	63,007
Investor loans secured by real estate | Multifamily
Allocation of allowance as well as the activity in allowance
Beginning ACL Balance	79,815	14,722	62,534	729
Initial ACL Recorded for PCD Loans		8,710		8,710
Charge-offs	0	0	0	0
Recoveries	0	0	0	0
Provision for Credit Losses	(20,756)	40,079	(3,475)	44,898
Ending ACL Balance	59,059	63,511	59,059	63,511
Investor loans secured by real estate | Construction and land
Allocation of allowance as well as the activity in allowance
Beginning ACL Balance	13,263	9,222	12,435	4,484
Initial ACL Recorded for PCD Loans		2,051		2,051
Charge-offs	0	0	0	0
Recoveries	0	0	0	0
Provision for Credit Losses	(3,715)	7,531	(2,887)	12,393
Ending ACL Balance	9,548	18,804	9,548	18,804
Investor loans secured by real estate | SBA secured by real estate
Allocation of allowance as well as the activity in allowance
Beginning ACL Balance	5,141	935	5,159	1,915
Initial ACL Recorded for PCD Loans		0		0
Charge-offs	0	(554)	(265)	(554)
Recoveries	0	0	0	0
Provision for Credit Losses	(460)	1,629	(213)	2,050
Ending ACL Balance	4,681	2,010	4,681	2,010
Business loans secured by real estate | SBA secured by real estate
Allocation of allowance as well as the activity in allowance
Beginning ACL Balance	6,451	4,044	6,567	2,119
Initial ACL Recorded for PCD Loans		235		235
Charge-offs	0	0	(98)	(315)
Recoveries	80	3	80	74
Provision for Credit Losses	(214)	86	(232)	48
Ending ACL Balance	6,317	4,368	6,317	4,368
Business loans secured by real estate | CRE owner-occupied
Allocation of allowance as well as the activity in allowance
Beginning ACL Balance	41,594	26,793	50,517	2,781
Initial ACL Recorded for PCD Loans		3,766		3,766
Charge-offs	0	0	0	0
Recoveries	15	11	30	23
Provision for Credit Losses	(5,862)	17,643	(14,800)	21,477
Ending ACL Balance	35,747	48,213	35,747	48,213
Business loans secured by real estate | Franchise real estate secured
Allocation of allowance as well as the activity in allowance
Beginning ACL Balance	10,876	7,503	11,451	592
Initial ACL Recorded for PCD Loans		0		0
Charge-offs	0	0	0	0
Recoveries	0	0	0	0
Provision for Credit Losses	560	5,557	(15)	7,269
Ending ACL Balance	11,436	13,060	11,436	13,060
Commercial loans | Commercial and industrial
Allocation of allowance as well as the activity in allowance
Beginning ACL Balance	43,373	15,742	46,964	13,857
Initial ACL Recorded for PCD Loans		2,325		2,325
Charge-offs	(3,290)	(2,286)	(4,569)	(2,776)
Recoveries	2,098	21	2,699	26
Provision for Credit Losses	(2,302)	26,165	(5,215)	28,448
Ending ACL Balance	39,879	41,967	39,879	41,967
Commercial loans | Franchise non-real estate secured
Allocation of allowance as well as the activity in allowance
Beginning ACL Balance	18,903	16,616	20,525	5,816
Initial ACL Recorded for PCD Loans		0		0
Charge-offs	0	(1,227)	(156)	(1,227)
Recoveries	0	0	0	0
Provision for Credit Losses	(1,590)	6,287	(3,056)	7,873
Ending ACL Balance	17,313	21,676	17,313	21,676
Commercial loans | SBA non-real estate secured
Allocation of allowance as well as the activity in allowance
Beginning ACL Balance	890	516	995	445
Initial ACL Recorded for PCD Loans		924		924
Charge-offs	0	(556)	0	(792)
Recoveries	2	(2)	4	2
Provision for Credit Losses	(162)	(282)	(269)	(197)
Ending ACL Balance	730	600	730	600
Retail loans | Single family residential
Allocation of allowance as well as the activity in allowance
Beginning ACL Balance	822	1,137	1,204	655
Initial ACL Recorded for PCD Loans		206		206
Charge-offs	0	(62)	0	(62)
Recoveries	1	1	1	1
Provision for Credit Losses	(153)	197	(535)	138
Ending ACL Balance	670	1,479	670	1,479
Retail loans | Consumer
Allocation of allowance as well as the activity in allowance
Beginning ACL Balance	326	2,296	491	406
Initial ACL Recorded for PCD Loans		0		0
Charge-offs	0	0	0	(8)
Recoveries	0	1	0	1
Provision for Credit Losses	(44)	1,279	(209)	1,195
Ending ACL Balance	$ 282	$ 3,576	$ 282	3,576
Cumulative Effect of the Change in Accounting Principle
Allocation of allowance as well as the activity in allowance
Beginning ACL Balance				55,686
Cumulative Effect of the Change in Accounting Principle | Investor loans secured by real estate | CRE non-owner-occupied
Allocation of allowance as well as the activity in allowance
Beginning ACL Balance				8,423
Cumulative Effect of the Change in Accounting Principle | Investor loans secured by real estate | Multifamily
Allocation of allowance as well as the activity in allowance
Beginning ACL Balance				9,174
Cumulative Effect of the Change in Accounting Principle | Investor loans secured by real estate | Construction and land
Allocation of allowance as well as the activity in allowance
Beginning ACL Balance				(124)
Cumulative Effect of the Change in Accounting Principle | Investor loans secured by real estate | SBA secured by real estate
Allocation of allowance as well as the activity in allowance
Beginning ACL Balance				(1,401)
Cumulative Effect of the Change in Accounting Principle | Business loans secured by real estate | SBA secured by real estate
Allocation of allowance as well as the activity in allowance
Beginning ACL Balance				2,207
Cumulative Effect of the Change in Accounting Principle | Business loans secured by real estate | CRE owner-occupied
Allocation of allowance as well as the activity in allowance
Beginning ACL Balance				20,166
Cumulative Effect of the Change in Accounting Principle | Business loans secured by real estate | Franchise real estate secured
Allocation of allowance as well as the activity in allowance
Beginning ACL Balance				5,199
Cumulative Effect of the Change in Accounting Principle | Commercial loans | Commercial and industrial
Allocation of allowance as well as the activity in allowance
Beginning ACL Balance				87
Cumulative Effect of the Change in Accounting Principle | Commercial loans | Franchise non-real estate secured
Allocation of allowance as well as the activity in allowance
Beginning ACL Balance				9,214
Cumulative Effect of the Change in Accounting Principle | Commercial loans | SBA non-real estate secured
Allocation of allowance as well as the activity in allowance
Beginning ACL Balance				218
Cumulative Effect of the Change in Accounting Principle | Retail loans | Single family residential
Allocation of allowance as well as the activity in allowance
Beginning ACL Balance				541
Cumulative Effect of the Change in Accounting Principle | Retail loans | Consumer
Allocation of allowance as well as the activity in allowance
Beginning ACL Balance				$ 1,982