Loans Receivable and Allowance for Credit Losses (Summary of Activities in Allowance for Loan Losses) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Allowance for loan losses
Allowance for loan losses, beginning of period	$ 585,724	$ 632,071	$ 619,983	$ 358,287
(Reversal of) provision for credit losses on loans	(11,736)	9,889	(19,459)	178,845
Gross charge-offs	(18,979)	(26,649)	(49,938)	(60,555)
Gross recoveries	5,465	2,441	9,743	16,209
Total net recoveries (charge-offs)	(13,514)	(24,208)	(40,195)	(44,346)
Foreign currency translation adjustment	(70)	500	75	308
Allowance for loan losses, end of period	560,404	618,252	560,404	618,252
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	362,528	380,723	398,040	238,376
(Reversal of) provision for credit losses on loans	(23,365)	31,691	(42,112)	130,171
Gross charge-offs	(1,154)	(25,111)	(20,162)	(57,466)
Gross recoveries	4,203	1,218	6,301	3,395
Total net recoveries (charge-offs)	3,049	(23,893)	(13,861)	(54,071)
Foreign currency translation adjustment	(70)	500	75	308
Allowance for loan losses, end of period	342,142	389,021	342,142	389,021
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	161,962	176,040	163,791	40,509
(Reversal of) provision for credit losses on loans	2,129	(8,301)	11,227	46,449
Gross charge-offs	(14,229)	(1,414)	(25,558)	(2,688)
Gross recoveries	187	485	589	10,371
Total net recoveries (charge-offs)	(14,042)	(929)	(24,969)	7,683
Foreign currency translation adjustment	0	0	0	0
Allowance for loan losses, end of period	150,049	166,810	150,049	166,810
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	21,925	25,058	27,573	22,826
(Reversal of) provision for credit losses on loans	(2,660)	(1,916)	(9,436)	7,273
Gross charge-offs	0	0	(130)	0
Gross recoveries	652	665	1,910	1,820
Total net recoveries (charge-offs)	652	665	1,780	1,820
Foreign currency translation adjustment	0	0	0	0
Allowance for loan losses, end of period	19,917	23,807	19,917	23,807
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	15,643	18,551	10,239	19,404
(Reversal of) provision for credit losses on loans	9,058	(8,180)	14,407	828
Gross charge-offs	(2,674)	0	(2,954)	0
Gross recoveries	267	30	602	58
Total net recoveries (charge-offs)	(2,407)	30	(2,352)	58
Foreign currency translation adjustment	0	0	0	0
Allowance for loan losses, end of period	22,294	10,401	22,294	10,401
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	16,530	25,314	15,520	28,527
(Reversal of) provision for credit losses on loans	2,537	(2,692)	3,522	(2,659)
Gross charge-offs	(912)	0	(1,046)	0
Gross recoveries	137	0	296	424
Total net recoveries (charge-offs)	(775)	0	(750)	424
Foreign currency translation adjustment	0	0	0	0
Allowance for loan losses, end of period	18,292	22,622	18,292	22,622
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	2,938	3,867	2,690	5,265
(Reversal of) provision for credit losses on loans	435	(637)	707	(20)
Gross charge-offs	0	0	(45)	(221)
Gross recoveries	19	43	40	47
Total net recoveries (charge-offs)	19	43	(5)	(174)
Foreign currency translation adjustment	0	0	0	0
Allowance for loan losses, end of period	3,392	3,273	3,392	3,273
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	4,198	2,518	2,130	3,380
(Reversal of) provision for credit losses on loans	130	(76)	2,226	(3,197)
Gross charge-offs	(10)	(124)	(43)	(180)
Gross recoveries	0	0	5	94
Total net recoveries (charge-offs)	(10)	(124)	(38)	(86)
Foreign currency translation adjustment	0	0	0	0
Allowance for loan losses, end of period	$ 4,318	$ 2,318	$ 4,318	2,318
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