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	Sep. 30, 2021	Dec. 31, 2020
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Current Fiscal Year	$ 8,122,458	$ 9,787,213
Fiscal Year before Current Fiscal Year	6,886,022	6,816,315
Two Years before Current Fiscal Year	5,487,019	5,125,324
Three Years before Current Fiscal Year	3,983,548	3,167,275
Four Years before Current Fiscal Year	2,563,182	1,547,971
Prior	3,953,468	3,277,221
Revolving Loans Amortized Cost Basis	9,222,611	8,390,152
Revolving Loans Converted to Term Loans Amortized Cost Basis	263,397	279,484
Total	40,481,705	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	5,973,751	7,390,682
Fiscal Year before Current Fiscal Year	4,664,319	5,000,429
Two Years before Current Fiscal Year	4,018,446	3,619,488
Three Years before Current Fiscal Year	2,810,180	2,129,478
Four Years before Current Fiscal Year	1,724,163	1,013,095
Prior	2,679,994	2,244,535
Revolving Loans Amortized Cost Basis	7,460,680	6,993,769
Revolving Loans Converted to Term Loans Amortized Cost Basis	35,480	48,551
Total	29,367,013	28,440,027
Commercial lending | Commercial and industrial (“C&I”)
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Current Fiscal Year	3,217,627	4,034,455
Fiscal Year before Current Fiscal Year	1,622,914	1,577,608
Two Years before Current Fiscal Year	915,627	562,750
Three Years before Current Fiscal Year	313,102	283,807
Four Years before Current Fiscal Year	189,682	75,933
Prior	250,461	253,079
Revolving Loans Amortized Cost Basis	7,293,183	6,814,607
Revolving Loans Converted to Term Loans Amortized Cost Basis	29,053	29,487
Total	13,831,649	13,631,726
Commercial lending | Commercial and industrial (“C&I”) | Pass
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Current Fiscal Year	3,136,513	3,912,147
Fiscal Year before Current Fiscal Year	1,454,547	1,477,740
Two Years before Current Fiscal Year	787,238	483,725
Three Years before Current Fiscal Year	279,254	245,594
Four Years before Current Fiscal Year	175,669	69,482
Prior	244,616	245,615
Revolving Loans Amortized Cost Basis	7,069,657	6,431,003
Revolving Loans Converted to Term Loans Amortized Cost Basis	29,053	29,487
Total	13,176,547	12,894,793
Commercial lending | Commercial and industrial (“C&I”) | Criticized (Accrual)
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Current Fiscal Year	75,943	120,183
Fiscal Year before Current Fiscal Year	168,029	74,601
Two Years before Current Fiscal Year	110,500	56,785
Three Years before Current Fiscal Year	13,700	19,426
Four Years before Current Fiscal Year	1,475	1,487
Prior	4,489	5,872
Revolving Loans Amortized Cost Basis	183,809	324,640
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	557,945	602,994
Commercial lending | Commercial and industrial (“C&I”) | Criticized (Nonaccrual)
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Current Fiscal Year	5,171	2,125
Fiscal Year before Current Fiscal Year	338	25,267
Two Years before Current Fiscal Year	17,889	22,240
Three Years before Current Fiscal Year	20,148	18,787
Four Years before Current Fiscal Year	12,538	4,964
Prior	1,356	1,592
Revolving Loans Amortized Cost Basis	39,717	58,964
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	97,157	133,939
Commercial lending | Commercial real estate (“CRE”)
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Current Fiscal Year	2,038,668	2,344,108
Fiscal Year before Current Fiscal Year	2,189,370	2,465,790
Two Years before Current Fiscal Year	2,297,907	2,396,262
Three Years before Current Fiscal Year	2,001,465	1,427,625
Four Years before Current Fiscal Year	1,210,948	734,788
Prior	1,925,203	1,613,707
Revolving Loans Amortized Cost Basis	148,077	173,267
Revolving Loans Converted to Term Loans Amortized Cost Basis	6,427	19,064
Total	11,818,065	11,174,611
Commercial lending | Commercial real estate (“CRE”) | Pass
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Current Fiscal Year	1,956,957	2,296,649
Fiscal Year before Current Fiscal Year	2,181,275	2,402,136
Two Years before Current Fiscal Year	2,288,701	2,310,748
Three Years before Current Fiscal Year	1,965,724	1,328,251
Four Years before Current Fiscal Year	1,181,060	732,694
Prior	1,869,183	1,529,681
Revolving Loans Amortized Cost Basis	148,077	173,267
Revolving Loans Converted to Term Loans Amortized Cost Basis	6,427	19,064
Total	11,597,404	10,792,490
Commercial lending | Commercial real estate (“CRE”) | Criticized (Accrual)
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Current Fiscal Year	77,286	47,459
Fiscal Year before Current Fiscal Year	8,095	63,654
Two Years before Current Fiscal Year	9,206	43,447
Three Years before Current Fiscal Year	31,093	98,259
Four Years before Current Fiscal Year	25,136	2,094
Prior	55,609	80,662
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	206,425	335,575
Commercial lending | Commercial real estate (“CRE”) | Criticized (Nonaccrual)
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Current Fiscal Year	4,425	0
Fiscal Year before Current Fiscal Year	0	0
Two Years before Current Fiscal Year	0	42,067
Three Years before Current Fiscal Year	4,648	1,115
Four Years before Current Fiscal Year	4,752	0
Prior	411	3,364
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	14,236	46,546
Commercial lending | Real estate loan | Multifamily residential
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Current Fiscal Year	611,439	783,671
Fiscal Year before Current Fiscal Year	752,178	784,324
Two Years before Current Fiscal Year	693,305	503,764
Three Years before Current Fiscal Year	456,471	418,046
Four Years before Current Fiscal Year	323,533	181,477
Prior	484,032	356,821
Revolving Loans Amortized Cost Basis	19,420	5,895
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	3,340,378	3,033,998
Commercial lending | Real estate loan | Multifamily residential | Pass
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Current Fiscal Year	611,439	783,671
Fiscal Year before Current Fiscal Year	752,178	783,589
Two Years before Current Fiscal Year	692,580	479,959
Three Years before Current Fiscal Year	432,959	411,945
Four Years before Current Fiscal Year	316,412	181,213
Prior	451,180	348,751
Revolving Loans Amortized Cost Basis	19,420	5,895
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	3,276,168	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	725	22,330
Three Years before Current Fiscal Year	23,512	6,101
Four Years before Current Fiscal Year	7,121	264
Prior	31,729	5,877
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	63,087	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	0	0
Four Years before Current Fiscal Year	0	0
Prior	1,123	2,193
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	1,123	3,668
Commercial lending | Construction and land
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Current Fiscal Year	106,017	228,448
Fiscal Year before Current Fiscal Year	99,857	172,707
Two Years before Current Fiscal Year	111,607	156,712
Three Years before Current Fiscal Year	39,142	0
Four Years before Current Fiscal Year	0	20,897
Prior	20,298	20,928
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	376,921	599,692
Commercial lending | Construction and land | Pass
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Current Fiscal Year	102,619	224,924
Fiscal Year before Current Fiscal Year	99,857	172,707
Two Years before Current Fiscal Year	111,607	156,712
Three Years before Current Fiscal Year	16,986	0
Four Years before Current Fiscal Year	0	20,897
Prior	1,252	1,028
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	332,321	576,268
Commercial lending | Construction and land | Criticized (Accrual)
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Current Fiscal Year	3,398	3,524
Fiscal Year before Current Fiscal Year	0	0
Two Years before Current Fiscal Year	0	0
Three Years before Current Fiscal Year	22,156	0
Four Years before Current Fiscal Year	0	0
Prior	19,046	19,900
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	44,600	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	0	0
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	0	0
Commercial lending | Total CRE
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Current Fiscal Year	2,756,124	3,356,227
Fiscal Year before Current Fiscal Year	3,041,405	3,422,821
Two Years before Current Fiscal Year	3,102,819	3,056,738
Three Years before Current Fiscal Year	2,497,078	1,845,671
Four Years before Current Fiscal Year	1,534,481	937,162
Prior	2,429,533	1,991,456
Revolving Loans Amortized Cost Basis	167,497	179,162
Revolving Loans Converted to Term Loans Amortized Cost Basis	6,427	19,064
Total	15,535,364	14,808,301
Consumer lending
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Current Fiscal Year	2,148,707	2,396,531
Fiscal Year before Current Fiscal Year	2,221,703	1,815,886
Two Years before Current Fiscal Year	1,468,573	1,505,836
Three Years before Current Fiscal Year	1,173,368	1,037,797
Four Years before Current Fiscal Year	839,019	534,876
Prior	1,273,474	1,032,686
Revolving Loans Amortized Cost Basis	1,761,931	1,396,383
Revolving Loans Converted to Term Loans Amortized Cost Basis	227,917	230,933
Total	11,114,692	9,950,928
Consumer lending | Real estate loan | Single-family residential
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Current Fiscal Year	2,131,943	2,385,853
Fiscal Year before Current Fiscal Year	2,214,522	1,814,855
Two Years before Current Fiscal Year	1,468,164	1,502,472
Three Years before Current Fiscal Year	1,171,685	1,023,496
Four Years before Current Fiscal Year	827,921	525,283
Prior	1,207,566	933,994
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	9,021,801	8,185,953
Consumer lending | Real estate loan | Single-family residential | Pass
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Current Fiscal Year	2,131,943	2,385,853
Fiscal Year before Current Fiscal Year	2,214,125	1,813,200
Two Years before Current Fiscal Year	1,465,612	1,501,660
Three Years before Current Fiscal Year	1,169,483	1,021,707
Four Years before Current Fiscal Year	825,120	523,170
Prior	1,203,031	921,714
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	9,009,314	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	0	1,429
Two Years before Current Fiscal Year	374	0
Three Years before Current Fiscal Year	490	0
Four Years before Current Fiscal Year	1,633	119
Prior	1,214	1,034
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	3,711	2,582
Consumer lending | Real estate loan | Single-family residential | Criticized (Nonaccrual)
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Current Fiscal Year	0	0
Fiscal Year before Current Fiscal Year	397	226
Two Years before Current Fiscal Year	2,178	812
Three Years before Current Fiscal Year	1,712	1,789
Four Years before Current Fiscal Year	1,168	1,994
Prior	3,321	11,246
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	8,776	16,067
Consumer lending | HELOCs
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Current Fiscal Year	27	1,131
Fiscal Year before Current Fiscal Year	1,799	1,031
Two Years before Current Fiscal Year	409	3,364
Three Years before Current Fiscal Year	1,683	9,980
Four Years before Current Fiscal Year	6,866	9,593
Prior	14,379	15,437
Revolving Loans Amortized Cost Basis	1,710,542	1,330,247
Revolving Loans Converted to Term Loans Amortized Cost Basis	227,917	230,933
Total	1,963,622	1,601,716
Consumer lending | HELOCs | Pass
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Current Fiscal Year	20	1,131
Fiscal Year before Current Fiscal Year	1,799	880
Two Years before Current Fiscal Year	258	2,879
Three Years before Current Fiscal Year	1,295	5,363
Four Years before Current Fiscal Year	3,343	8,433
Prior	12,578	13,475
Revolving Loans Amortized Cost Basis	1,710,540	1,328,919
Revolving Loans Converted to Term Loans Amortized Cost Basis	223,057	225,810
Total	1,952,890	1,586,890
Consumer lending | HELOCs | Criticized (Accrual)
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Current Fiscal Year	7	0
Fiscal Year before Current Fiscal Year	0	0
Two Years before Current Fiscal Year	0	200
Three Years before Current Fiscal Year	200	0
Four Years before Current Fiscal Year	0	996
Prior	222	0
Revolving Loans Amortized Cost Basis	2	1,328
Revolving Loans Converted to Term Loans Amortized Cost Basis	1,570	606
Total	2,001	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	151	285
Three Years before Current Fiscal Year	188	4,617
Four Years before Current Fiscal Year	3,523	164
Prior	1,579	1,962
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	3,290	4,517
Total	8,731	11,696
Consumer lending | Total residential mortgage
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Current Fiscal Year	2,131,970	2,386,984
Fiscal Year before Current Fiscal Year	2,216,321	1,815,886
Two Years before Current Fiscal Year	1,468,573	1,505,836
Three Years before Current Fiscal Year	1,173,368	1,033,476
Four Years before Current Fiscal Year	834,787	534,876
Prior	1,221,945	949,431
Revolving Loans Amortized Cost Basis	1,710,542	1,330,247
Revolving Loans Converted to Term Loans Amortized Cost Basis	227,917	230,933
Total	10,985,423	9,787,669
Consumer lending | Other consumer
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Current Fiscal Year	16,737	9,547
Fiscal Year before Current Fiscal Year	5,382	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	51,529	83,255
Revolving Loans Amortized Cost Basis	51,389	66,136
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	129,269	163,259
Consumer lending | Other consumer | Pass
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Current Fiscal Year	16,737	9,531
Fiscal Year before Current Fiscal Year	5,382	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	51,529	83,255
Revolving Loans Amortized Cost Basis	51,389	66,136
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	126,778	160,752
Consumer lending | Other consumer | Criticized (Accrual)
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
Current Fiscal Year	0	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	0	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	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	$ 2,491	$ 2,491