Loans Receivable and Allowance for Credit Losses (Summary of Activities in Allowance for Loan Losses by Portfolio Segments and Unfunded Credit Commitments) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Financing Receivable Allowance for Credit Losses
Accounting Standards Update [Extensible List]			us-gaap:AccountingStandardsUpdate201613Member
Allowance for loan losses by portfolio segments
Allowance, beginning of period			$ 358,287
Provision for (reversal of) credit losses	$ 10,000	$ 38,284	186,313	$ 80,108
Gross charge-offs	(2,800)	(36)	(2,800)	(426)
Allowance, end of period	618,252		618,252
Allowance for unfunded credit commitments
Provision for credit losses on unfunded credit commitments	10,000	38,284	186,313	80,108
PCD or PCI loans
Allowance for loan losses by portfolio segments
Allowance, beginning of period			0
Unfunded Credit Commitments
Allowance for loan losses by portfolio segments
Provision for (reversal of) credit losses	111	405	7,468	858
Allowance for unfunded credit commitments
Allowance for Unfunded Credit Commitments	28,972	13,019	11,158	12,566
Provision for credit losses on unfunded credit commitments	111	405	7,468	858
Allowance for Unfunded Credit Commitments	29,083	13,424	29,083	13,424
Unfunded Credit Commitments | Cumulative Effect, Period Of Adoption, Adjustment
Allowance for unfunded credit commitments
Allowance for Unfunded Credit Commitments	0	0	10,457	0
Commercial lending | Commercial and industrial (“C&I”)
Allowance for loan losses by portfolio segments
Allowance, beginning of period	380,723	205,503	238,376	189,117
Provision for (reversal of) credit losses	31,691	37,281	130,171	78,685
Gross charge-offs	(25,111)	(25,098)	(57,466)	(54,087)
Gross recoveries	1,218	1,648	3,395	5,612
Total net (charge-offs) recoveries	(23,893)	(23,450)	(54,071)	(48,475)
Foreign currency translation adjustment	500	(465)	308	(458)
Allowance, end of period	389,021	218,869	389,021	218,869
Allowance for unfunded credit commitments
Provision for credit losses on unfunded credit commitments	31,691	37,281	130,171	78,685
Commercial lending | Commercial and industrial (“C&I”) | Cumulative Effect, Period Of Adoption, Adjustment
Allowance for loan losses by portfolio segments
Allowance, beginning of period			74,237
Commercial lending | Commercial and industrial (“C&I”) | Cumulative Effect, Period of Adoption, Adjusted Balance
Allowance for loan losses by portfolio segments
Allowance, beginning of period			312,613
Commercial lending | Commercial real estate (“CRE”)
Allowance for loan losses by portfolio segments
Allowance, beginning of period	176,040	39,811	40,509	40,666
Provision for (reversal of) credit losses	(8,301)	(3,213)	46,449	(6,127)
Gross charge-offs	(1,414)	(1,021)	(2,688)	(1,021)
Gross recoveries	485	1,896	10,371	3,955
Total net (charge-offs) recoveries	(929)	875	7,683	2,934
Foreign currency translation adjustment		0	0	0
Allowance, end of period	166,810	37,473	166,810	37,473
Allowance for unfunded credit commitments
Provision for credit losses on unfunded credit commitments	(8,301)	(3,213)	46,449	(6,127)
Commercial lending | Commercial real estate (“CRE”) | Cumulative Effect, Period Of Adoption, Adjustment
Allowance for loan losses by portfolio segments
Allowance, beginning of period			72,169
Commercial lending | Commercial real estate (“CRE”) | Cumulative Effect, Period of Adoption, Adjusted Balance
Allowance for loan losses by portfolio segments
Allowance, beginning of period			112,678
Commercial lending | Real estate loan | Multifamily residential
Allowance for loan losses by portfolio segments
Allowance, beginning of period	25,058	19,280	22,826	19,885
Provision for (reversal of) credit losses	(1,916)	985	7,273	46
Gross charge-offs	0	0	0	0
Gross recoveries	665	42	1,820	376
Total net (charge-offs) recoveries	665	42	1,820	376
Foreign currency translation adjustment		0	0	0
Allowance, end of period	23,807	20,307	23,807	20,307
Allowance for unfunded credit commitments
Provision for credit losses on unfunded credit commitments	(1,916)	985	7,273	46
Commercial lending | Real estate loan | Multifamily residential | Cumulative Effect, Period Of Adoption, Adjustment
Allowance for loan losses by portfolio segments
Allowance, beginning of period			(8,112)
Commercial lending | Real estate loan | Multifamily residential | Cumulative Effect, Period of Adoption, Adjusted Balance
Allowance for loan losses by portfolio segments
Allowance, beginning of period			14,714
Commercial lending | Construction and land
Allowance for loan losses by portfolio segments
Allowance, beginning of period	18,551	22,961	19,404	20,290
Provision for (reversal of) credit losses	(8,180)	6,189	828	8,358
Gross charge-offs	0	0	0	0
Gross recoveries	30	21	58	523
Total net (charge-offs) recoveries	30	21	58	523
Foreign currency translation adjustment		0	0	0
Allowance, end of period	10,401	29,171	10,401	29,171
Allowance for unfunded credit commitments
Provision for credit losses on unfunded credit commitments	(8,180)	6,189	828	8,358
Commercial lending | Construction and land | Cumulative Effect, Period Of Adoption, Adjustment
Allowance for loan losses by portfolio segments
Allowance, beginning of period			(9,889)
Commercial lending | Construction and land | Cumulative Effect, Period of Adoption, Adjusted Balance
Allowance for loan losses by portfolio segments
Allowance, beginning of period			9,515
Consumer lending | Real estate loan | Single-family residential
Allowance for loan losses by portfolio segments
Allowance, beginning of period	25,314	32,763	28,527	31,340
Provision for (reversal of) credit losses	(2,692)	(2,877)	(2,659)	(1,528)
Gross charge-offs	0	(11)	0	(11)
Gross recoveries	0	60	424	134
Total net (charge-offs) recoveries	0	49	424	123
Foreign currency translation adjustment		0	0	0
Allowance, end of period	22,622	29,935	22,622	29,935
Allowance for unfunded credit commitments
Provision for credit losses on unfunded credit commitments	(2,692)	(2,877)	(2,659)	(1,528)
Consumer lending | Real estate loan | Single-family residential | Cumulative Effect, Period Of Adoption, Adjustment
Allowance for loan losses by portfolio segments
Allowance, beginning of period			(3,670)
Consumer lending | Real estate loan | Single-family residential | Cumulative Effect, Period of Adoption, Adjusted Balance
Allowance for loan losses by portfolio segments
Allowance, beginning of period			24,857
Consumer lending | HELOCs
Allowance for loan losses by portfolio segments
Allowance, beginning of period	3,867	6,177	5,265	5,774
Provision for (reversal of) credit losses	(637)	(326)	(20)	75
Gross charge-offs	0	0	(221)	0
Gross recoveries	43	5	47	7
Total net (charge-offs) recoveries	43	5	(174)	7
Foreign currency translation adjustment		0	0	0
Allowance, end of period	3,273	5,856	3,273	5,856
Allowance for unfunded credit commitments
Provision for credit losses on unfunded credit commitments	(637)	(326)	(20)	75
Consumer lending | HELOCs | Cumulative Effect, Period Of Adoption, Adjustment
Allowance for loan losses by portfolio segments
Allowance, beginning of period			(1,798)
Consumer lending | HELOCs | Cumulative Effect, Period of Adoption, Adjusted Balance
Allowance for loan losses by portfolio segments
Allowance, beginning of period			3,467
Consumer lending | Other consumer
Allowance for loan losses by portfolio segments
Allowance, beginning of period	2,518	4,130	3,380	4,250
Provision for (reversal of) credit losses	(76)	(160)	(3,197)	(259)
Gross charge-offs	(124)	(12)	(180)	(40)
Gross recoveries	0	7	94	14
Total net (charge-offs) recoveries	(124)	(5)	(86)	(26)
Foreign currency translation adjustment		0	0	0
Allowance, end of period	2,318	3,965	2,318	3,965
Allowance for unfunded credit commitments
Provision for credit losses on unfunded credit commitments	(76)	(160)	(3,197)	(259)
Consumer lending | Other consumer | Cumulative Effect, Period Of Adoption, Adjustment
Allowance for loan losses by portfolio segments
Allowance, beginning of period			2,221
Consumer lending | Other consumer | Cumulative Effect, Period of Adoption, Adjusted Balance
Allowance for loan losses by portfolio segments
Allowance, beginning of period			5,601
Commercial and consumer lending
Allowance for loan losses by portfolio segments
Allowance, beginning of period	632,071	330,625	358,287	311,322
Provision for (reversal of) credit losses	9,889	37,879	178,845	79,250
Gross charge-offs	(26,649)	(26,142)	(60,555)	(55,159)
Gross recoveries	2,441	3,679	16,209	10,621
Total net (charge-offs) recoveries	(24,208)	(22,463)	(44,346)	(44,538)
Foreign currency translation adjustment	500	(465)	308	(458)
Allowance, end of period	618,252	345,576	618,252	345,576
Allowance for unfunded credit commitments
Provision for credit losses on unfunded credit commitments	$ 9,889	$ 37,879	178,845	$ 79,250
Commercial and consumer lending | Cumulative Effect, Period Of Adoption, Adjustment
Allowance for loan losses by portfolio segments
Allowance, beginning of period			125,158
Commercial and consumer lending | Cumulative Effect, Period of Adoption, Adjusted Balance
Allowance for loan losses by portfolio segments
Allowance, beginning of period			$ 483,445