Loans Receivable and Allowance for Credit Losses (Aging Analysis on Loans Held-for-Investment) (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Nonaccrual and Past Due Loans
Current accruing loans	$ 39,269,817	$ 38,125,211
Total Accruing Past Due Loans	86,969	50,590
Total Nonaccrual Loans	231,962	215,154
Total	39,588,748	38,390,955
Accruing Loans 30-59  Days Past Due
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	43,943	44,136
Accruing Loans 60-89  Days Past Due
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	43,026	6,454
Commercial lending
Nonaccrual and Past Due Loans
Current accruing loans	28,898,105	28,224,064
Total Accruing Past Due Loans	71,545	31,810
Total Nonaccrual Loans	200,263	184,153
Total	29,169,913	28,440,027
Commercial lending | Commercial and industrial (“C&I”)
Nonaccrual and Past Due Loans
Current accruing loans	13,923,524	13,488,070
Total Accruing Past Due Loans	32,050	9,717
Total Nonaccrual Loans	125,536	133,939
Total	14,081,110	13,631,726
Commercial lending | Commercial real estate (“CRE”)
Nonaccrual and Past Due Loans
Current accruing loans	11,473,405	11,127,690
Total Accruing Past Due Loans	39,495	375
Total Nonaccrual Loans	50,134	46,546
Total	11,563,034	11,174,611
Commercial lending | Real estate loan | Multifamily residential
Nonaccrual and Past Due Loans
Current accruing loans	3,061,822	3,028,512
Total Accruing Past Due Loans	0	1,818
Total Nonaccrual Loans	4,693	3,668
Total	3,066,515	3,033,998
Commercial lending | Construction and land
Nonaccrual and Past Due Loans
Current accruing loans	439,354	579,792
Total Accruing Past Due Loans	0	19,900
Total Nonaccrual Loans	19,900	0
Total	459,254	599,692
Commercial lending | Total CRE
Nonaccrual and Past Due Loans
Current accruing loans	14,974,581	14,735,994
Total Accruing Past Due Loans	39,495	22,093
Total Nonaccrual Loans	74,727	50,214
Total	15,088,803	14,808,301
Commercial lending | Accruing Loans 30-59  Days Past Due
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	32,105	31,086
Commercial lending | Accruing Loans 30-59  Days Past Due | Commercial and industrial (“C&I”)
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	26,417	8,993
Commercial lending | Accruing Loans 30-59  Days Past Due | Commercial real estate (“CRE”)
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	5,688	375
Commercial lending | Accruing Loans 30-59  Days Past Due | Real estate loan | Multifamily residential
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	0	1,818
Commercial lending | Accruing Loans 30-59  Days Past Due | Construction and land
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	0	19,900
Commercial lending | Accruing Loans 30-59  Days Past Due | Total CRE
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	5,688	22,093
Commercial lending | Accruing Loans 60-89  Days Past Due
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	39,440	724
Commercial lending | Accruing Loans 60-89  Days Past Due | Commercial and industrial (“C&I”)
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	5,633	724
Commercial lending | Accruing Loans 60-89  Days Past Due | Commercial real estate (“CRE”)
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	33,807	0
Commercial lending | Accruing Loans 60-89  Days Past Due | Real estate loan | Multifamily residential
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	0	0
Commercial lending | Accruing Loans 60-89  Days Past Due | Construction and land
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	0	0
Commercial lending | Accruing Loans 60-89  Days Past Due | Total CRE
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	33,807	0
Consumer lending
Nonaccrual and Past Due Loans
Current accruing loans	10,371,712	9,901,147
Total Accruing Past Due Loans	15,424	18,780
Total Nonaccrual Loans	31,699	31,001
Total	10,418,835	9,950,928
Consumer lending | Real estate loan | Single-family residential
Nonaccrual and Past Due Loans
Current accruing loans	8,493,416	8,156,645
Total Accruing Past Due Loans	12,575	12,494
Total Nonaccrual Loans	18,296	16,814
Total	8,524,287	8,185,953
Consumer lending | HELOCs
Nonaccrual and Past Due Loans
Current accruing loans	1,735,692	1,583,968
Total Accruing Past Due Loans	2,603	6,052
Total Nonaccrual Loans	10,877	11,696
Total	1,749,172	1,601,716
Consumer lending | Total residential mortgage
Nonaccrual and Past Due Loans
Current accruing loans	10,229,108	9,740,613
Total Accruing Past Due Loans	15,178	18,546
Total Nonaccrual Loans	29,173	28,510
Total	10,273,459	9,787,669
Consumer lending | Other consumer
Nonaccrual and Past Due Loans
Current accruing loans	142,604	160,534
Total Accruing Past Due Loans	246	234
Total Nonaccrual Loans	2,526	2,491
Total	145,376	163,259
Consumer lending | Accruing Loans 30-59  Days Past Due
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	11,838	13,050
Consumer lending | Accruing Loans 30-59  Days Past Due | Real estate loan | Single-family residential
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	9,827	9,911
Consumer lending | Accruing Loans 30-59  Days Past Due | HELOCs
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	1,769	2,922
Consumer lending | Accruing Loans 30-59  Days Past Due | Total residential mortgage
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	11,596	12,833
Consumer lending | Accruing Loans 30-59  Days Past Due | Other consumer
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	242	217
Consumer lending | Accruing Loans 60-89  Days Past Due
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	3,586	5,730
Consumer lending | Accruing Loans 60-89  Days Past Due | Real estate loan | Single-family residential
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	2,748	2,583
Consumer lending | Accruing Loans 60-89  Days Past Due | HELOCs
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	834	3,130
Consumer lending | Accruing Loans 60-89  Days Past Due | Total residential mortgage
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	3,582	5,713
Consumer lending | Accruing Loans 60-89  Days Past Due | Other consumer
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	$ 4	$ 17