Loans Receivable and Allowance for Credit Losses (Summary of Activities in Allowance for Loan Losses) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Allowance for loan losses
Allowance for loan losses, beginning of period	$ 607,506	$ 557,003	$ 619,983	$ 358,287
(Reversal of) provision for credit losses on loans	(8,771)	94,300	(7,723)	168,956
Gross charge-offs	(15,060)	(20,949)	(30,959)	(33,906)
Gross recoveries	1,785	1,709	4,278	13,768
Total net (charge-offs) recoveries	(13,275)	(19,240)	(26,681)	(20,138)
Foreign currency translation adjustment	264	8	145	(192)
Allowance for loan losses, end of period	585,724	632,071	585,724	632,071
Cumulative Effect, Period Of Adoption, Adjustment | ASU 2016-13
Allowance for loan losses
Allowance for loan losses, beginning of period				125,158
Cumulative Effect, Period of Adoption, Adjusted Balance | ASU 2016-13
Allowance for loan losses
Allowance for loan losses, beginning of period				483,445
Commercial lending | Commercial and industrial (“C&I”)
Allowance for loan losses
Allowance for loan losses, beginning of period	394,084	362,629	398,040	238,376
(Reversal of) provision for credit losses on loans	(22,586)	37,862	(18,747)	98,480
Gross charge-offs	(10,572)	(20,378)	(19,008)	(32,355)
Gross recoveries	1,338	602	2,098	2,177
Total net (charge-offs) recoveries	(9,234)	(19,776)	(16,910)	(30,178)
Foreign currency translation adjustment	264	8	145	(192)
Allowance for loan losses, end of period	362,528	380,723	362,528	380,723
Commercial lending | Commercial and industrial (“C&I”) | Cumulative Effect, Period Of Adoption, Adjustment | ASU 2016-13
Allowance for loan losses
Allowance for loan losses, beginning of period				74,237
Commercial lending | Commercial and industrial (“C&I”) | Cumulative Effect, Period of Adoption, Adjusted Balance | ASU 2016-13
Allowance for loan losses
Allowance for loan losses, beginning of period				312,613
Commercial lending | Commercial real estate (“CRE”)
Allowance for loan losses
Allowance for loan losses, beginning of period	146,399	132,819	163,791	40,509
(Reversal of) provision for credit losses on loans	19,375	43,315	9,098	54,750
Gross charge-offs	(4,134)	(320)	(11,329)	(1,274)
Gross recoveries	322	226	402	9,886
Total net (charge-offs) recoveries	(3,812)	(94)	(10,927)	8,612
Foreign currency translation adjustment	0	0	0	0
Allowance for loan losses, end of period	161,962	176,040	161,962	176,040
Commercial lending | Commercial real estate (“CRE”) | Cumulative Effect, Period Of Adoption, Adjustment | ASU 2016-13
Allowance for loan losses
Allowance for loan losses, beginning of period				72,169
Commercial lending | Commercial real estate (“CRE”) | Cumulative Effect, Period of Adoption, Adjusted Balance | ASU 2016-13
Allowance for loan losses
Allowance for loan losses, beginning of period				112,678
Commercial lending | Residential loan | Multifamily residential
Allowance for loan losses
Allowance for loan losses, beginning of period	27,407	16,530	27,573	22,826
(Reversal of) provision for credit losses on loans	(5,385)	7,908	(6,776)	9,189
Gross charge-offs	(113)	0	(130)	0
Gross recoveries	16	620	1,258	1,155
Total net (charge-offs) recoveries	(97)	620	1,128	1,155
Foreign currency translation adjustment	0	0	0	0
Allowance for loan losses, end of period	21,925	25,058	21,925	25,058
Commercial lending | Residential loan | Multifamily residential | Cumulative Effect, Period Of Adoption, Adjustment | ASU 2016-13
Allowance for loan losses
Allowance for loan losses, beginning of period				(8,112)
Commercial lending | Residential loan | Multifamily residential | Cumulative Effect, Period of Adoption, Adjusted Balance | ASU 2016-13
Allowance for loan losses
Allowance for loan losses, beginning of period				14,714
Commercial lending | Construction and land
Allowance for loan losses
Allowance for loan losses, beginning of period	19,089	11,018	10,239	19,404
(Reversal of) provision for credit losses on loans	(3,243)	7,526	5,349	9,008
Gross charge-offs	(209)	0	(280)	0
Gross recoveries	6	7	335	28
Total net (charge-offs) recoveries	(203)	7	55	28
Foreign currency translation adjustment	0	0	0	0
Allowance for loan losses, end of period	15,643	18,551	15,643	18,551
Commercial lending | Construction and land | Cumulative Effect, Period Of Adoption, Adjustment | ASU 2016-13
Allowance for loan losses
Allowance for loan losses, beginning of period				(9,889)
Commercial lending | Construction and land | Cumulative Effect, Period of Adoption, Adjusted Balance | ASU 2016-13
Allowance for loan losses
Allowance for loan losses, beginning of period				9,515
Consumer lending | Residential loan | Single-family residential
Allowance for loan losses
Allowance for loan losses, beginning of period	15,839	26,822	15,520	28,527
(Reversal of) provision for credit losses on loans	609	(1,667)	985	33
Gross charge-offs	0	0	(134)	0
Gross recoveries	82	159	159	424
Total net (charge-offs) recoveries	82	159	25	424
Foreign currency translation adjustment	0	0	0	0
Allowance for loan losses, end of period	16,530	25,314	16,530	25,314
Consumer lending | Residential loan | Single-family residential | Cumulative Effect, Period Of Adoption, Adjustment | ASU 2016-13
Allowance for loan losses
Allowance for loan losses, beginning of period				(3,670)
Consumer lending | Residential loan | Single-family residential | Cumulative Effect, Period of Adoption, Adjusted Balance | ASU 2016-13
Allowance for loan losses
Allowance for loan losses, beginning of period				24,857
Consumer lending | HELOCs
Allowance for loan losses
Allowance for loan losses, beginning of period	2,670	3,881	2,690	5,265
(Reversal of) provision for credit losses on loans	250	205	272	617
Gross charge-offs	0	(221)	(45)	(221)
Gross recoveries	18	2	21	4
Total net (charge-offs) recoveries	18	(219)	(24)	(217)
Foreign currency translation adjustment	0	0	0	0
Allowance for loan losses, end of period	2,938	3,867	2,938	3,867
Consumer lending | HELOCs | Cumulative Effect, Period Of Adoption, Adjustment | ASU 2016-13
Allowance for loan losses
Allowance for loan losses, beginning of period				(1,798)
Consumer lending | HELOCs | Cumulative Effect, Period of Adoption, Adjusted Balance | ASU 2016-13
Allowance for loan losses
Allowance for loan losses, beginning of period				3,467
Consumer lending | Other consumer
Allowance for loan losses
Allowance for loan losses, beginning of period	2,018	3,304	2,130	3,380
(Reversal of) provision for credit losses on loans	2,209	(849)	2,096	(3,121)
Gross charge-offs	(32)	(30)	(33)	(56)
Gross recoveries	3	93	5	94
Total net (charge-offs) recoveries	(29)	63	(28)	38
Foreign currency translation adjustment	0	0	0	0
Allowance for loan losses, end of period	$ 4,198	$ 2,518	$ 4,198	2,518
Consumer lending | Other consumer | Cumulative Effect, Period Of Adoption, Adjustment | ASU 2016-13
Allowance for loan losses
Allowance for loan losses, beginning of period				2,221
Consumer lending | Other consumer | Cumulative Effect, Period of Adoption, Adjusted Balance | ASU 2016-13
Allowance for loan losses
Allowance for loan losses, beginning of period				$ 5,601