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	Dec. 31, 2021	Dec. 31, 2020
Financing Receivable, Credit Quality Indicator [Line Items]
2021	$ 10,680,884	$ 9,787,213
2020	6,294,357	6,816,315
2019	5,104,045	5,125,324
2018	3,678,223	3,167,275
2017	2,400,331	1,547,971
Prior	3,686,038	3,277,221
Revolving Loans Amortized Cost Basis	9,612,862	8,390,152
Revolving Loans Converted to Term Loans Amortized Cost Basis	237,041	279,484
Loans held-for-investment	41,693,781	38,390,955
Pass [Member] | Federal Housing Administration Loan
Financing Receivable, Credit Quality Indicator [Line Items]
Nonaccrual loans guaranteed by the FHA	1,600	747
Commercial Lending
Financing Receivable, Credit Quality Indicator [Line Items]
2021	8,046,445	7,390,682
2020	4,177,452	5,000,429
2019	3,721,211	3,619,488
2018	2,590,956	2,129,478
2017	1,622,234	1,013,095
Prior	2,486,373	2,244,535
Revolving Loans Amortized Cost Basis	7,647,844	6,993,769
Revolving Loans Converted to Term Loans Amortized Cost Basis	35,231	48,551
Loans held-for-investment	30,327,746	28,440,027
Commercial Lending | C&I
Financing Receivable, Credit Quality Indicator [Line Items]
2021	4,026,214	4,034,455
2020	1,253,234	1,577,608
2019	701,797	562,750
2018	239,265	283,807
2017	156,829	75,933
Prior	245,775	253,079
Revolving Loans Amortized Cost Basis	7,498,652	6,814,607
Revolving Loans Converted to Term Loans Amortized Cost Basis	28,842	29,487
Loans held-for-investment	14,150,608	13,631,726
Commercial Lending | C&I | Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	3,911,722	3,912,147
2020	1,133,085	1,477,740
2019	629,007	483,725
2018	187,195	245,594
2017	132,392	69,482
Prior	225,326	245,615
Revolving Loans Amortized Cost Basis	7,383,485	6,431,003
Revolving Loans Converted to Term Loans Amortized Cost Basis	28,842	29,487
Loans held-for-investment	13,631,054	12,894,793
Commercial Lending | C&I | Criticized (accrual)
Financing Receivable, Credit Quality Indicator [Line Items]
2021	85,036	120,183
2020	117,357	74,601
2019	72,277	56,785
2018	51,553	19,426
2017	15,136	1,487
Prior	4,005	5,872
Revolving Loans Amortized Cost Basis	115,167	324,640
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Loans held-for-investment	460,531	602,994
Commercial Lending | C&I | Criticized (nonaccrual)
Financing Receivable, Credit Quality Indicator [Line Items]
2021	29,456	2,125
2020	2,792	25,267
2019	513	22,240
2018	517	18,787
2017	9,301	4,964
Prior	16,444	1,592
Revolving Loans Amortized Cost Basis	0	58,964
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Loans held-for-investment	59,023	133,939
Commercial Lending | CRE
Financing Receivable, Credit Quality Indicator [Line Items]
2021	2,867,598	2,344,108
2020	2,093,703	2,465,790
2019	2,239,696	2,396,262
2018	1,884,558	1,427,625
2017	1,150,285	734,788
Prior	1,784,150	1,613,707
Revolving Loans Amortized Cost Basis	128,668	173,267
Revolving Loans Converted to Term Loans Amortized Cost Basis	6,389	19,064
Loans held-for-investment	12,155,047	11,174,611
Commercial Lending | CRE | Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	2,792,193	2,296,649
2020	2,090,503	2,402,136
2019	2,230,520	2,310,748
2018	1,863,481	1,328,251
2017	1,120,682	732,694
Prior	1,727,862	1,529,681
Revolving Loans Amortized Cost Basis	128,668	173,267
Revolving Loans Converted to Term Loans Amortized Cost Basis	6,389	19,064
Loans held-for-investment	11,960,298	10,792,490
Commercial Lending | CRE | Criticized (accrual)
Financing Receivable, Credit Quality Indicator [Line Items]
2021	71,055	47,459
2020	3,200	63,654
2019	9,176	43,447
2018	21,077	98,259
2017	24,851	2,094
Prior	55,892	80,662
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Loans held-for-investment	185,251	335,575
Commercial Lending | CRE | Criticized (nonaccrual)
Financing Receivable, Credit Quality Indicator [Line Items]
2021	4,350	0
2020	0	0
2019	0	42,067
2018	0	1,115
2017	4,752	0
Prior	396	3,364
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Loans held-for-investment	9,498	46,546
Commercial Lending | Real estate loan | Multifamily
Financing Receivable, Credit Quality Indicator [Line Items]
2021	1,026,295	783,671
2020	726,772	784,324
2019	689,174	503,764
2018	441,663	418,046
2017	315,120	181,477
Prior	456,057	356,821
Revolving Loans Amortized Cost Basis	20,524	5,895
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Loans held-for-investment	3,675,605	3,033,998
Commercial Lending | Real estate loan | Multifamily | Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	1,026,295	783,671
2020	726,772	783,589
2019	688,453	479,959
2018	419,319	411,945
2017	308,087	181,213
Prior	424,947	348,751
Revolving Loans Amortized Cost Basis	20,524	5,895
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Loans held-for-investment	3,614,397	2,995,023
Commercial Lending | Real estate loan | Multifamily | Criticized (accrual)
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0	0
2020	0	735
2019	721	22,330
2018	22,344	6,101
2017	7,033	264
Prior	30,666	5,877
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Loans held-for-investment	60,764	35,307
Commercial Lending | Real estate loan | Multifamily | Criticized (nonaccrual)
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0	0
2020	0	0
2019	0	1,475
2018	0	0
2017	0	0
Prior	444	2,193
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Loans held-for-investment	444	3,668
Commercial Lending | Construction and land
Financing Receivable, Credit Quality Indicator [Line Items]
2021	126,338	228,448
2020	103,743	172,707
2019	90,544	156,712
2018	25,470	0
2017	0	20,897
Prior	391	20,928
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Loans held-for-investment	346,486	599,692
Commercial Lending | Construction and land | Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	122,983	224,924
2020	103,743	172,707
2019	90,544	156,712
2018	3,412	0
2017	0	20,897
Prior	391	1,028
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Loans held-for-investment	321,073	576,268
Commercial Lending | Construction and land | Criticized (accrual)
Financing Receivable, Credit Quality Indicator [Line Items]
2021	3,355	3,524
2020	0	0
2019	0	0
2018	22,058	0
2017	0	0
Prior	0	19,900
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Loans held-for-investment	25,413	23,424
Commercial Lending | Construction and land | Criticized (nonaccrual)
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0	0
2020	0	0
2019	0	0
2018	0	0
2017	0	0
Prior	0	0
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Loans held-for-investment	0	0
Commercial Lending | Total CRE
Financing Receivable, Credit Quality Indicator [Line Items]
2021	4,020,231	3,356,227
2020	2,924,218	3,422,821
2019	3,019,414	3,056,738
2018	2,351,691	1,845,671
2017	1,465,405	937,162
Prior	2,240,598	1,991,456
Revolving Loans Amortized Cost Basis	149,192	179,162
Revolving Loans Converted to Term Loans Amortized Cost Basis	6,389	19,064
Loans held-for-investment	16,177,138	14,808,301
Consumer Lending
Financing Receivable, Credit Quality Indicator [Line Items]
2021	2,634,439	2,396,531
2020	2,116,905	1,815,886
2019	1,382,834	1,505,836
2018	1,087,267	1,037,797
2017	778,097	534,876
Prior	1,199,665	1,032,686
Revolving Loans Amortized Cost Basis	1,965,018	1,396,383
Revolving Loans Converted to Term Loans Amortized Cost Basis	201,810	230,933
Loans held-for-investment	11,366,035	9,950,928
Consumer Lending | Real estate loan | Single-family
Financing Receivable, Credit Quality Indicator [Line Items]
2021	2,616,958	2,385,853
2020	2,108,370	1,814,855
2019	1,378,138	1,502,472
2018	1,085,732	1,023,496
2017	769,545	525,283
Prior	1,134,959	933,994
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Loans held-for-investment	9,093,702	8,185,953
Consumer Lending | Real estate loan | Single-family | Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	2,616,958	2,385,853
2020	2,108,370	1,813,200
2019	1,375,929	1,501,660
2018	1,079,030	1,021,707
2017	763,351	523,170
Prior	1,127,516	921,714
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Loans held-for-investment	9,071,154	8,167,304
Consumer Lending | Real estate loan | Single-family | Criticized (accrual)
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0	0
2020	0	1,429
2019	458	0
2018	2,813	0
2017	1,899	119
Prior	3,212	1,034
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Loans held-for-investment	8,382	2,582
Consumer Lending | Real estate loan | Single-family | Criticized (nonaccrual)
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0	0
2020	0	226
2019	1,751	812
2018	3,889	1,789
2017	4,295	1,994
Prior	4,231	11,246
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Loans held-for-investment	14,166	16,067
Consumer Lending | HELOCs
Financing Receivable, Credit Quality Indicator [Line Items]
2021	648	1,131
2020	3,277	1,031
2019	4,696	3,364
2018	1,535	9,980
2017	6,811	9,593
Prior	12,559	15,437
Revolving Loans Amortized Cost Basis	1,913,485	1,330,247
Revolving Loans Converted to Term Loans Amortized Cost Basis	201,810	230,933
Loans held-for-investment	2,144,821	1,601,716
Consumer Lending | HELOCs | Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	648	1,131
2020	3,277	880
2019	4,644	2,879
2018	1,347	5,363
2017	3,268	8,433
Prior	11,215	13,475
Revolving Loans Amortized Cost Basis	1,913,478	1,328,919
Revolving Loans Converted to Term Loans Amortized Cost Basis	197,414	225,810
Loans held-for-investment	2,135,291	1,586,890
Consumer Lending | HELOCs | Criticized (accrual)
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0	0
2020	0	0
2019	0	200
2018	0	0
2017	0	996
Prior	371	0
Revolving Loans Amortized Cost Basis	7	1,328
Revolving Loans Converted to Term Loans Amortized Cost Basis	708	606
Loans held-for-investment	1,086	3,130
Consumer Lending | HELOCs | Criticized (nonaccrual)
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0	0
2020	0	151
2019	52	285
2018	188	4,617
2017	3,543	164
Prior	973	1,962
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	3,688	4,517
Loans held-for-investment	8,444	11,696
Consumer Lending | Total residential mortgage
Financing Receivable, Credit Quality Indicator [Line Items]
2021	2,617,606	2,386,984
2020	2,111,647	1,815,886
2019	1,382,834	1,505,836
2018	1,087,267	1,033,476
2017	776,356	534,876
Prior	1,147,518	949,431
Revolving Loans Amortized Cost Basis	1,913,485	1,330,247
Revolving Loans Converted to Term Loans Amortized Cost Basis	201,810	230,933
Loans held-for-investment	11,238,523	9,787,669
Consumer Lending | Other consumer
Financing Receivable, Credit Quality Indicator [Line Items]
2021	16,833	9,547
2020	5,258	0
2019	0	0
2018	0	4,321
2017	1,741	0
Prior	52,147	83,255
Revolving Loans Amortized Cost Basis	51,533	66,136
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Loans held-for-investment	127,512	163,259
Consumer Lending | Other consumer | Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2021	16,831	9,531
2020	5,258	0
2019	0	0
2018	0	1,830
2017	1,741	0
Prior	52,147	83,255
Revolving Loans Amortized Cost Basis	51,481	66,136
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Loans held-for-investment	127,458	160,752
Consumer Lending | Other consumer | Criticized (accrual)
Financing Receivable, Credit Quality Indicator [Line Items]
2021	2	16
2020	0	0
2019	0	0
2018	0	0
2017	0	0
Prior	0	0
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Loans held-for-investment	2	16
Consumer Lending | Other consumer | Criticized (nonaccrual)
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0	0
2020	0	0
2019	0	0
2018	0	2,491
2017	0	0
Prior	0	0
Revolving Loans Amortized Cost Basis	52	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Loans held-for-investment	$ 52	$ 2,491