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, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Allowance for loan losses
Allowance for loan losses, beginning of period	$ 563,270	$ 585,724	$ 541,579	$ 619,983
Provision for (reversal of) credit losses on loans	27,274	(11,735)	51,995	(19,474)
Gross charge-offs	(13,905)	(18,979)	(26,684)	(49,938)
Gross recoveries	7,264	5,465	18,363	9,743
Total net recoveries (charge-offs)	(6,641)	(13,514)	(8,321)	(40,195)
Foreign currency translation adjustment	(1,386)	(71)	(2,736)	90
Allowance for loan losses, end of period	582,517	560,404	582,517	560,404
Commercial lending | Commercial and industrial (“C&I”)
Allowance for loan losses
Allowance for loan losses, beginning of period	363,282	362,528	338,252	398,040
Provision for (reversal of) credit losses on loans	9,575	(23,364)	37,867	(42,127)
Gross charge-offs	(6,894)	(1,154)	(18,322)	(20,162)
Gross recoveries	7,172	4,203	16,688	6,301
Total net recoveries (charge-offs)	278	3,049	(1,634)	(13,861)
Foreign currency translation adjustment	(1,386)	(71)	(2,736)	90
Allowance for loan losses, end of period	371,749	342,142	371,749	342,142
Commercial lending | Commercial real estate (“CRE”)
Allowance for loan losses
Allowance for loan losses, beginning of period	140,245	161,962	150,940	163,791
Provision for (reversal of) credit losses on loans	5,299	2,129	(5,013)	11,227
Gross charge-offs	(288)	(14,229)	(1,357)	(25,558)
Gross recoveries	45	187	731	589
Total net recoveries (charge-offs)	(243)	(14,042)	(626)	(24,969)
Foreign currency translation adjustment	0	0	0	0
Allowance for loan losses, end of period	145,301	150,049	145,301	150,049
Commercial lending | Residential loan | Multifamily residential
Allowance for loan losses
Allowance for loan losses, beginning of period	26,552	21,925	14,400	27,573
Provision for (reversal of) credit losses on loans	5,047	(2,660)	16,680	(9,436)
Gross charge-offs	(5,938)	0	(5,947)	(130)
Gross recoveries	19	652	547	1,910
Total net recoveries (charge-offs)	(5,919)	652	(5,400)	1,780
Foreign currency translation adjustment	0	0	0	0
Allowance for loan losses, end of period	25,680	19,917	25,680	19,917
Commercial lending | Construction and land
Allowance for loan losses
Allowance for loan losses, beginning of period	6,682	15,643	15,468	10,239
Provision for (reversal of) credit losses on loans	817	9,058	(8,027)	14,407
Gross charge-offs	0	(2,674)	0	(2,954)
Gross recoveries	7	267	65	602
Total net recoveries (charge-offs)	7	(2,407)	65	(2,352)
Foreign currency translation adjustment	0	0	0	0
Allowance for loan losses, end of period	7,506	22,294	7,506	22,294
Consumer lending | Residential loan | Single-family residential
Allowance for loan losses
Allowance for loan losses, beginning of period	21,840	16,530	17,160	15,520
Provision for (reversal of) credit losses on loans	6,182	2,537	10,569	3,522
Gross charge-offs	(775)	(912)	(775)	(1,046)
Gross recoveries	16	137	309	296
Total net recoveries (charge-offs)	(759)	(775)	(466)	(750)
Foreign currency translation adjustment	0	0	0	0
Allowance for loan losses, end of period	27,263	18,292	27,263	18,292
Consumer lending | HELOCs
Allowance for loan losses
Allowance for loan losses, beginning of period	3,220	2,938	3,435	2,690
Provision for (reversal of) credit losses on loans	99	435	59	707
Gross charge-offs	0	0	(193)	(45)
Gross recoveries	5	19	23	40
Total net recoveries (charge-offs)	5	19	(170)	(5)
Foreign currency translation adjustment	0	0	0	0
Allowance for loan losses, end of period	3,324	3,392	3,324	3,392
Consumer lending | Other consumer
Allowance for loan losses
Allowance for loan losses, beginning of period	1,449	4,198	1,924	2,130
Provision for (reversal of) credit losses on loans	255	130	(140)	2,226
Gross charge-offs	(10)	(10)	(90)	(43)
Gross recoveries	0	0	0	5
Total net recoveries (charge-offs)	(10)	(10)	(90)	(38)
Foreign currency translation adjustment	0	0	0	0
Allowance for loan losses, end of period	$ 1,694	$ 4,318	$ 1,694	$ 4,318