Loans Receivable and Allowance for Credit Losses (Credit Risk Ratings and/or Vintage Years for Loans Held-for-Investment by Portfolio Segment) (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Current Fiscal Year	$ 5,908,830	$ 9,787,213
Fiscal Year before Current Fiscal Year	7,688,732	6,816,315
Two Years before Current Fiscal Year	5,963,358	5,125,324
Three Years before Current Fiscal Year	4,435,471	3,167,275
Four Years before Current Fiscal Year	2,733,322	1,547,971
Prior	4,280,854	3,277,221
Revolving Loans Amortized Cost Basis	8,756,455	8,390,152
Revolving Loans Converted to Term Loans Amortized Cost Basis	304,477	279,484
Total	40,071,499	38,390,955
Federal Housing Administration Loan
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Financing receivable, recorded investment, 90 days past due and still accruing, classified as pass	647	747
Commercial lending
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Current Fiscal Year	4,376,921	7,390,682
Fiscal Year before Current Fiscal Year	5,359,896	5,000,429
Two Years before Current Fiscal Year	4,392,351	3,619,488
Three Years before Current Fiscal Year	3,155,950	2,129,478
Four Years before Current Fiscal Year	1,839,800	1,013,095
Prior	2,890,575	2,244,535
Revolving Loans Amortized Cost Basis	7,113,563	6,993,769
Revolving Loans Converted to Term Loans Amortized Cost Basis	53,248	48,551
Total	29,182,304	28,440,027
Commercial lending | Commercial and industrial (“C&I”)
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Current Fiscal Year	2,553,506	4,034,455
Fiscal Year before Current Fiscal Year	2,249,548	1,577,608
Two Years before Current Fiscal Year	1,152,728	562,750
Three Years before Current Fiscal Year	368,014	283,807
Four Years before Current Fiscal Year	216,643	75,933
Prior	267,472	253,079
Revolving Loans Amortized Cost Basis	6,953,375	6,814,607
Revolving Loans Converted to Term Loans Amortized Cost Basis	29,175	29,487
Total	13,790,461	13,631,726
Commercial lending | Commercial and industrial (“C&I”) | Pass
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Current Fiscal Year	2,473,716	3,912,147
Fiscal Year before Current Fiscal Year	2,133,586	1,477,740
Two Years before Current Fiscal Year	1,062,978	483,725
Three Years before Current Fiscal Year	333,190	245,594
Four Years before Current Fiscal Year	200,711	69,482
Prior	261,156	245,615
Revolving Loans Amortized Cost Basis	6,706,592	6,431,003
Revolving Loans Converted to Term Loans Amortized Cost Basis	29,175	29,487
Total	13,201,104	12,894,793
Commercial lending | Commercial and industrial (“C&I”) | Criticized (Accrual)
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Current Fiscal Year	63,030	120,183
Fiscal Year before Current Fiscal Year	115,148	74,601
Two Years before Current Fiscal Year	87,636	56,785
Three Years before Current Fiscal Year	13,847	19,426
Four Years before Current Fiscal Year	3,184	1,487
Prior	4,939	5,872
Revolving Loans Amortized Cost Basis	218,348	324,640
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	506,132	602,994
Commercial lending | Commercial and industrial (“C&I”) | Criticized (Nonaccrual)
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Current Fiscal Year	16,760	2,125
Fiscal Year before Current Fiscal Year	814	25,267
Two Years before Current Fiscal Year	2,114	22,240
Three Years before Current Fiscal Year	20,977	18,787
Four Years before Current Fiscal Year	12,748	4,964
Prior	1,377	1,592
Revolving Loans Amortized Cost Basis	28,435	58,964
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	83,225	133,939
Commercial lending | Commercial real estate (“CRE”)
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Current Fiscal Year	1,381,266	2,344,108
Fiscal Year before Current Fiscal Year	2,229,224	2,465,790
Two Years before Current Fiscal Year	2,364,424	2,396,262
Three Years before Current Fiscal Year	2,198,614	1,427,625
Four Years before Current Fiscal Year	1,278,421	734,788
Prior	2,081,589	1,613,707
Revolving Loans Amortized Cost Basis	153,758	173,267
Revolving Loans Converted to Term Loans Amortized Cost Basis	24,073	19,064
Total	11,711,369	11,174,611
Commercial lending | Commercial real estate (“CRE”) | Pass
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Current Fiscal Year	1,296,562	2,296,649
Fiscal Year before Current Fiscal Year	2,215,380	2,402,136
Two Years before Current Fiscal Year	2,316,293	2,310,748
Three Years before Current Fiscal Year	2,142,042	1,328,251
Four Years before Current Fiscal Year	1,239,195	732,694
Prior	2,021,101	1,529,681
Revolving Loans Amortized Cost Basis	153,758	173,267
Revolving Loans Converted to Term Loans Amortized Cost Basis	24,073	19,064
Total	11,408,404	10,792,490
Commercial lending | Commercial real estate (“CRE”) | Criticized (Accrual)
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Current Fiscal Year	80,204	47,459
Fiscal Year before Current Fiscal Year	13,844	63,654
Two Years before Current Fiscal Year	48,131	43,447
Three Years before Current Fiscal Year	9,743	98,259
Four Years before Current Fiscal Year	33,358	2,094
Prior	58,905	80,662
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	244,185	335,575
Commercial lending | Commercial real estate (“CRE”) | Criticized (Nonaccrual)
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Current Fiscal Year	4,500	0
Fiscal Year before Current Fiscal Year	0	0
Two Years before Current Fiscal Year	0	42,067
Three Years before Current Fiscal Year	46,829	1,115
Four Years before Current Fiscal Year	5,868	0
Prior	1,583	3,364
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	58,780	46,546
Commercial lending | Real estate loan | Multifamily residential
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Current Fiscal Year	384,655	783,671
Fiscal Year before Current Fiscal Year	760,226	784,324
Two Years before Current Fiscal Year	744,497	503,764
Three Years before Current Fiscal Year	478,210	418,046
Four Years before Current Fiscal Year	344,736	181,477
Prior	501,042	356,821
Revolving Loans Amortized Cost Basis	6,430	5,895
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	3,219,796	3,033,998
Commercial lending | Real estate loan | Multifamily residential | Pass
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Current Fiscal Year	384,655	783,671
Fiscal Year before Current Fiscal Year	760,226	783,589
Two Years before Current Fiscal Year	743,769	479,959
Three Years before Current Fiscal Year	454,684	411,945
Four Years before Current Fiscal Year	338,701	181,213
Prior	469,340	348,751
Revolving Loans Amortized Cost Basis	6,430	5,895
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	3,157,805	2,995,023
Commercial lending | Real estate loan | Multifamily residential | Criticized (Accrual)
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Current Fiscal Year	0	0
Fiscal Year before Current Fiscal Year	0	735
Two Years before Current Fiscal Year	728	22,330
Three Years before Current Fiscal Year	22,337	6,101
Four Years before Current Fiscal Year	6,035	264
Prior	29,998	5,877
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	59,098	35,307
Commercial lending | Real estate loan | Multifamily residential | Criticized (Nonaccrual)
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Current Fiscal Year	0	0
Fiscal Year before Current Fiscal Year	0	0
Two Years before Current Fiscal Year	0	1,475
Three Years before Current Fiscal Year	1,189	0
Four Years before Current Fiscal Year	0	0
Prior	1,704	2,193
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	2,893	3,668
Commercial lending | Construction and land
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Current Fiscal Year	57,494	228,448
Fiscal Year before Current Fiscal Year	120,898	172,707
Two Years before Current Fiscal Year	130,702	156,712
Three Years before Current Fiscal Year	111,112	0
Four Years before Current Fiscal Year	0	20,897
Prior	40,472	20,928
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	460,678	599,692
Commercial lending | Construction and land | Pass
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Current Fiscal Year	54,054	224,924
Fiscal Year before Current Fiscal Year	120,898	172,707
Two Years before Current Fiscal Year	130,702	156,712
Three Years before Current Fiscal Year	111,112	0
Four Years before Current Fiscal Year	0	20,897
Prior	1,421	1,028
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	418,187	576,268
Commercial lending | Construction and land | Criticized (Accrual)
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Current Fiscal Year	3,440	3,524
Fiscal Year before Current Fiscal Year	0	0
Two Years before Current Fiscal Year	0	0
Three Years before Current Fiscal Year	0	0
Four Years before Current Fiscal Year	0	0
Prior	19,151	19,900
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	22,591	23,424
Commercial lending | Construction and land | Criticized (Nonaccrual)
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Current Fiscal Year	0	0
Fiscal Year before Current Fiscal Year	0	0
Two Years before Current Fiscal Year	0	0
Three Years before Current Fiscal Year	0	0
Four Years before Current Fiscal Year	0	0
Prior	19,900	0
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	19,900	0
Commercial lending | Total CRE
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Current Fiscal Year	1,823,415	3,356,227
Fiscal Year before Current Fiscal Year	3,110,348	3,422,821
Two Years before Current Fiscal Year	3,239,623	3,056,738
Three Years before Current Fiscal Year	2,787,936	1,845,671
Four Years before Current Fiscal Year	1,623,157	937,162
Prior	2,623,103	1,991,456
Revolving Loans Amortized Cost Basis	160,188	179,162
Revolving Loans Converted to Term Loans Amortized Cost Basis	24,073	19,064
Total	15,391,843	14,808,301
Consumer lending
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Current Fiscal Year	1,531,909	2,396,531
Fiscal Year before Current Fiscal Year	2,328,836	1,815,886
Two Years before Current Fiscal Year	1,571,007	1,505,836
Three Years before Current Fiscal Year	1,279,521	1,037,797
Four Years before Current Fiscal Year	893,522	534,876
Prior	1,390,279	1,032,686
Revolving Loans Amortized Cost Basis	1,642,892	1,396,383
Revolving Loans Converted to Term Loans Amortized Cost Basis	251,229	230,933
Total	10,889,195	9,950,928
Consumer lending | Real estate loan | Single-family residential
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Current Fiscal Year	1,527,794	2,385,853
Fiscal Year before Current Fiscal Year	2,319,670	1,814,855
Two Years before Current Fiscal Year	1,568,888	1,502,472
Three Years before Current Fiscal Year	1,277,308	1,023,496
Four Years before Current Fiscal Year	881,249	525,283
Prior	1,294,461	933,994
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	8,869,370	8,185,953
Consumer lending | Real estate loan | Single-family residential | Pass
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Current Fiscal Year	1,526,669	2,385,853
Fiscal Year before Current Fiscal Year	2,319,273	1,813,200
Two Years before Current Fiscal Year	1,567,312	1,501,660
Three Years before Current Fiscal Year	1,273,541	1,021,707
Four Years before Current Fiscal Year	879,004	523,170
Prior	1,282,396	921,714
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	8,848,195	8,167,304
Consumer lending | Real estate loan | Single-family residential | Criticized (Accrual)
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Current Fiscal Year	0	0
Fiscal Year before Current Fiscal Year	397	1,429
Two Years before Current Fiscal Year	156	0
Three Years before Current Fiscal Year	1,100	0
Four Years before Current Fiscal Year	0	119
Prior	0	1,034
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	1,653	2,582
Consumer lending | Real estate loan | Single-family residential | Criticized (Nonaccrual)
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Current Fiscal Year	1,125	0
Fiscal Year before Current Fiscal Year	0	226
Two Years before Current Fiscal Year	1,420	812
Three Years before Current Fiscal Year	2,667	1,789
Four Years before Current Fiscal Year	2,245	1,994
Prior	12,065	11,246
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	19,522	16,067
Consumer lending | HELOCs
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Current Fiscal Year	0	1,131
Fiscal Year before Current Fiscal Year	1,938	1,031
Two Years before Current Fiscal Year	2,119	3,364
Three Years before Current Fiscal Year	2,213	9,980
Four Years before Current Fiscal Year	8,041	9,593
Prior	13,912	15,437
Revolving Loans Amortized Cost Basis	1,592,714	1,330,247
Revolving Loans Converted to Term Loans Amortized Cost Basis	251,229	230,933
Total	1,872,166	1,601,716
Consumer lending | HELOCs | Pass
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Current Fiscal Year	0	1,131
Fiscal Year before Current Fiscal Year	1,938	880
Two Years before Current Fiscal Year	1,501	2,879
Three Years before Current Fiscal Year	1,824	5,363
Four Years before Current Fiscal Year	4,508	8,433
Prior	11,385	13,475
Revolving Loans Amortized Cost Basis	1,592,348	1,328,919
Revolving Loans Converted to Term Loans Amortized Cost Basis	247,174	225,810
Total	1,860,678	1,586,890
Consumer lending | HELOCs | Criticized (Accrual)
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Current Fiscal Year	0	0
Fiscal Year before Current Fiscal Year	0	0
Two Years before Current Fiscal Year	0	200
Three Years before Current Fiscal Year	201	0
Four Years before Current Fiscal Year	0	996
Prior	600	0
Revolving Loans Amortized Cost Basis	366	1,328
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	606
Total	1,167	3,130
Consumer lending | HELOCs | Criticized (Nonaccrual)
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Current Fiscal Year	0	0
Fiscal Year before Current Fiscal Year	0	151
Two Years before Current Fiscal Year	618	285
Three Years before Current Fiscal Year	188	4,617
Four Years before Current Fiscal Year	3,533	164
Prior	1,927	1,962
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	4,055	4,517
Total	10,321	11,696
Consumer lending | Total residential mortgage
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Current Fiscal Year	1,527,794	2,386,984
Fiscal Year before Current Fiscal Year	2,321,608	1,815,886
Two Years before Current Fiscal Year	1,571,007	1,505,836
Three Years before Current Fiscal Year	1,279,521	1,033,476
Four Years before Current Fiscal Year	889,290	534,876
Prior	1,308,373	949,431
Revolving Loans Amortized Cost Basis	1,592,714	1,330,247
Revolving Loans Converted to Term Loans Amortized Cost Basis	251,229	230,933
Total	10,741,536	9,787,669
Consumer lending | Other consumer
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Current Fiscal Year	4,115	9,547
Fiscal Year before Current Fiscal Year	7,228	0
Two Years before Current Fiscal Year	0	0
Three Years before Current Fiscal Year	0	4,321
Four Years before Current Fiscal Year	4,232	0
Prior	81,906	83,255
Revolving Loans Amortized Cost Basis	50,178	66,136
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	147,659	163,259
Consumer lending | Other consumer | Pass
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Current Fiscal Year	4,096	9,531
Fiscal Year before Current Fiscal Year	7,228	0
Two Years before Current Fiscal Year	0	0
Three Years before Current Fiscal Year	0	1,830
Four Years before Current Fiscal Year	1,741	0
Prior	81,906	83,255
Revolving Loans Amortized Cost Basis	50,166	66,136
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	145,137	160,752
Consumer lending | Other consumer | Criticized (Accrual)
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Current Fiscal Year	19	16
Fiscal Year before Current Fiscal Year	0	0
Two Years before Current Fiscal Year	0	0
Three Years before Current Fiscal Year	0	0
Four Years before Current Fiscal Year	0	0
Prior	0	0
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	19	16
Consumer lending | Other consumer | Criticized (Nonaccrual)
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Current Fiscal Year	0	0
Fiscal Year before Current Fiscal Year	0	0
Two Years before Current Fiscal Year	0	0
Three Years before Current Fiscal Year	0	2,491
Four Years before Current Fiscal Year	2,491	0
Prior	0	0
Revolving Loans Amortized Cost Basis	12	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	$ 2,503	$ 2,491