Loans Receivable and Allowance for Credit Losses (Summary of Activities in Allowance for Loan Losses) (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020
Allowance for loan losses
Allowance for loan losses, beginning of period	$ 619,983	$ 358,287
Provision for (reversal of) credit losses on loans	1,048	74,656
Gross charge-offs	(15,899)	(12,957)
Gross recoveries	2,493	12,059
Total net (charge-offs) recoveries	(13,406)	(898)
Foreign currency translation adjustment	(119)	(200)
Allowance for loan losses, end of period	607,506	557,003
Cumulative Effect, Period Of Adoption, Adjustment \| ASU 2016-13
Allowance for loan losses
Allowance for loan losses, beginning of period		125,158
Commercial lending \| Commercial and industrial (“C&I”)
Allowance for loan losses
Allowance for loan losses, beginning of period	398,040	238,376
Provision for (reversal of) credit losses on loans	3,839	60,618
Gross charge-offs	(8,436)	(11,977)
Gross recoveries	760	1,575
Total net (charge-offs) recoveries	(7,676)	(10,402)
Foreign currency translation adjustment	(119)	(200)
Allowance for loan losses, end of period	394,084	362,629
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 real estate (“CRE”)
Allowance for loan losses
Allowance for loan losses, beginning of period	163,791	40,509
Provision for (reversal of) credit losses on loans	(10,277)	11,435
Gross charge-offs	(7,195)	(954)
Gross recoveries	80	9,660
Total net (charge-offs) recoveries	(7,115)	8,706
Foreign currency translation adjustment	0	0
Allowance for loan losses, end of period	146,399	132,819
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 \| Residential loan \| Multifamily residential
Allowance for loan losses
Allowance for loan losses, beginning of period	27,573	22,826
Provision for (reversal of) credit losses on loans	(1,391)	1,281
Gross charge-offs	(17)	0
Gross recoveries	1,242	535
Total net (charge-offs) recoveries	1,225	535
Foreign currency translation adjustment	0	0
Allowance for loan losses, end of period	27,407	16,530
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 \| Construction and land
Allowance for loan losses
Allowance for loan losses, beginning of period	10,239	19,404
Provision for (reversal of) credit losses on loans	8,592	1,482
Gross charge-offs	(71)	0
Gross recoveries	329	21
Total net (charge-offs) recoveries	258	21
Foreign currency translation adjustment	0	0
Allowance for loan losses, end of period	19,089	11,018
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)
Consumer lending \| Residential loan \| Single-family residential
Allowance for loan losses
Allowance for loan losses, beginning of period	15,520	28,527
Provision for (reversal of) credit losses on loans	376	1,700
Gross charge-offs	(134)	0
Gross recoveries	77	265
Total net (charge-offs) recoveries	(57)	265
Foreign currency translation adjustment	0	0
Allowance for loan losses, end of period	15,839	26,822
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 \| HELOCs
Allowance for loan losses
Allowance for loan losses, beginning of period	2,690	5,265
Provision for (reversal of) credit losses on loans	22	412
Gross charge-offs	(45)	0
Gross recoveries	3	2
Total net (charge-offs) recoveries	(42)	2
Foreign currency translation adjustment	0	0
Allowance for loan losses, end of period	2,670	3,881
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 \| Other consumer
Allowance for loan losses
Allowance for loan losses, beginning of period	2,130	3,380
Provision for (reversal of) credit losses on loans	(113)	(2,272)
Gross charge-offs	(1)	(26)
Gross recoveries	2	1
Total net (charge-offs) recoveries	1	(25)
Foreign currency translation adjustment	0	0
Allowance for loan losses, end of period	$ 2,018	3,304
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

Financing Receivable, Allowance for Credit Loss, Write Off, Net Of Recovery

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Provision for (Reversal of) Credit Losses on Loans and Provision for Loan Losses

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Amount of foreign currency translation gain (loss) which (increases) decreases allowance for credit loss on financing receivable.

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Amount of allowance for credit loss on financing receivable. Excludes allowance for financing receivable covered under loss sharing agreement.

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Amount of writeoff of financing receivable, charged against allowance for credit loss.

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