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	Mar. 31, 2022	Dec. 31, 2021
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2022	$ 2,806,876	$ 10,680,884
2021	10,041,197	6,294,357
2020	5,860,687	5,104,045
2019	4,833,251	3,678,223
2018	3,471,721	2,400,331
Prior	5,674,225	3,686,038
Revolving Loans	10,588,172	9,612,862
Revolving Loans Converted to Term Loans	214,553	237,041
Total	43,490,682	41,693,781
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	1,100	1,600
Commercial lending
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2022	2,213,577	8,046,445
2021	7,412,709	4,177,452
2020	3,844,305	3,721,211
2019	3,557,109	2,590,956
2018	2,465,555	1,622,234
Prior	3,811,364	2,486,373
Revolving Loans	8,473,629	7,647,844
Revolving Loans Converted to Term Loans	34,972	35,231
Total	31,813,220	30,327,746
Commercial lending | Commercial and industrial (“C&I”)
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2022	789,201	4,026,214
2021	3,479,193	1,253,234
2020	1,049,700	701,797
2019	620,907	239,265
2018	237,564	156,829
Prior	336,548	245,775
Revolving Loans	8,296,400	7,498,652
Revolving Loans Converted to Term Loans	28,621	28,842
Total	14,838,134	14,150,608
Commercial lending | Commercial and industrial (“C&I”) | Pass
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2022	737,607	3,911,722
2021	3,443,409	1,133,085
2020	983,506	629,007
2019	571,374	187,195
2018	188,189	132,392
Prior	303,396	225,326
Revolving Loans	8,203,700	7,383,485
Revolving Loans Converted to Term Loans	28,621	28,842
Total	14,459,802	13,631,054
Commercial lending | Commercial and industrial (“C&I”) | Criticized (Accrual)
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2022	51,594	85,036
2021	22,381	117,357
2020	60,176	72,277
2019	49,533	51,553
2018	43,741	15,136
Prior	20,353	4,005
Revolving Loans	78,781	115,167
Revolving Loans Converted to Term Loans	0	0
Total	326,559	460,531
Commercial lending | Commercial and industrial (“C&I”) | Criticized (Nonaccrual)
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2022	0	29,456
2021	13,403	2,792
2020	6,018	513
2019	0	517
2018	5,634	9,301
Prior	12,799	16,444
Revolving Loans	13,919	0
Revolving Loans Converted to Term Loans	0	0
Total	51,773	59,023
Commercial lending | Commercial real estate (“CRE”)
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2022	1,034,550	2,867,598
2021	2,756,868	2,093,703
2020	1,997,821	2,239,696
2019	2,163,183	1,884,558
2018	1,793,441	1,150,285
Prior	2,727,048	1,784,150
Revolving Loans	157,525	128,668
Revolving Loans Converted to Term Loans	6,351	6,389
Total	12,636,787	12,155,047
Commercial lending | Commercial real estate (“CRE”) | Pass
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2022	1,029,501	2,792,193
2021	2,646,859	2,090,503
2020	1,993,446	2,230,520
2019	2,108,508	1,863,481
2018	1,737,301	1,120,682
Prior	2,628,811	1,727,862
Revolving Loans	157,525	128,668
Revolving Loans Converted to Term Loans	6,351	6,389
Total	12,308,302	11,960,298
Commercial lending | Commercial real estate (“CRE”) | Criticized (Accrual)
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2022	5,049	71,055
2021	105,708	3,200
2020	4,375	9,176
2019	54,675	21,077
2018	56,140	24,851
Prior	93,134	55,892
Revolving Loans	0	0
Revolving Loans Converted to Term Loans	0	0
Total	319,081	185,251
Commercial lending | Commercial real estate (“CRE”) | Criticized (Nonaccrual)
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2022	0	4,350
2021	4,301	0
2020	0	0
2019	0	0
2018	0	4,752
Prior	5,103	396
Revolving Loans	0	0
Revolving Loans Converted to Term Loans	0	0
Total	9,404	9,498
Commercial lending | Real estate loan | Multifamily residential
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2022	354,628	1,026,295
2021	980,895	726,772
2020	698,645	689,174
2019	683,867	441,663
2018	409,226	315,120
Prior	747,498	456,057
Revolving Loans	19,704	20,524
Revolving Loans Converted to Term Loans	0	0
Total	3,894,463	3,675,605
Commercial lending | Real estate loan | Multifamily residential | Pass
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2022	354,628	1,026,295
2021	980,895	726,772
2020	698,645	688,453
2019	683,149	419,319
2018	386,920	308,087
Prior	709,085	424,947
Revolving Loans	19,704	20,524
Revolving Loans Converted to Term Loans	0	0
Total	3,833,026	3,614,397
Commercial lending | Real estate loan | Multifamily residential | Criticized (Accrual)
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2022	0	0
2021	0	0
2020	0	721
2019	718	22,344
2018	22,306	7,033
Prior	37,990	30,666
Revolving Loans	0	0
Revolving Loans Converted to Term Loans	0	0
Total	61,014	60,764
Commercial lending | Real estate loan | Multifamily residential | Criticized (Nonaccrual)
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2022	0	0
2021	0	0
2020	0	0
2019	0	0
2018	0	0
Prior	423	444
Revolving Loans	0	0
Revolving Loans Converted to Term Loans	0	0
Total	423	444
Commercial lending | Construction and land
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2022	35,198	126,338
2021	195,753	103,743
2020	98,139	90,544
2019	89,152	25,470
2018	25,324	0
Prior	270	391
Revolving Loans	0	0
Revolving Loans Converted to Term Loans	0	0
Total	443,836	346,486
Commercial lending | Construction and land | Pass
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2022	35,198	122,983
2021	192,442	103,743
2020	93,792	90,544
2019	89,152	3,412
2018	3,370	0
Prior	270	391
Revolving Loans	0	0
Revolving Loans Converted to Term Loans	0	0
Total	414,224	321,073
Commercial lending | Construction and land | Criticized (Accrual)
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2022	0	3,355
2021	3,311	0
2020	4,347	0
2019	0	22,058
2018	21,954	0
Prior	0	0
Revolving Loans	0	0
Revolving Loans Converted to Term Loans	0	0
Total	29,612	25,413
Commercial lending | Construction and land | Criticized (Nonaccrual)
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2022	0	0
2021	0	0
2020	0	0
2019	0	0
2018	0	0
Prior	0	0
Revolving Loans	0	0
Revolving Loans Converted to Term Loans	0	0
Total	0	0
Commercial lending | Total CRE
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2022	1,424,376	4,020,231
2021	3,933,516	2,924,218
2020	2,794,605	3,019,414
2019	2,936,202	2,351,691
2018	2,227,991	1,465,405
Prior	3,474,816	2,240,598
Revolving Loans	177,229	149,192
Revolving Loans Converted to Term Loans	6,351	6,389
Total	16,975,086	16,177,138
Consumer lending
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2022	593,299	2,634,439
2021	2,628,488	2,116,905
2020	2,016,382	1,382,834
2019	1,276,142	1,087,267
2018	1,006,166	778,097
Prior	1,862,861	1,199,665
Revolving Loans	2,114,543	1,965,018
Revolving Loans Converted to Term Loans	179,581	201,810
Total	11,677,462	11,366,035
Consumer lending | Real estate loan | Single-family residential
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2022	592,760	2,616,958
2021	2,610,335	2,108,370
2020	2,007,368	1,378,138
2019	1,274,332	1,085,732
2018	1,004,517	769,545
Prior	1,794,117	1,134,959
Revolving Loans	0	0
Revolving Loans Converted to Term Loans	0	0
Total	9,283,429	9,093,702
Consumer lending | Real estate loan | Single-family residential | Pass
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2022	592,760	2,616,958
2021	2,610,094	2,108,370
2020	2,006,265	1,375,929
2019	1,271,347	1,079,030
2018	996,334	763,351
Prior	1,780,965	1,127,516
Revolving Loans	0	0
Revolving Loans Converted to Term Loans	0	0
Total	9,257,765	9,071,154
Consumer lending | Real estate loan | Single-family residential | Criticized (Accrual)
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2022	0	0
2021	241	0
2020	706	458
2019	961	2,813
2018	4,281	1,899
Prior	4,187	3,212
Revolving Loans	0	0
Revolving Loans Converted to Term Loans	0	0
Total	10,376	8,382
Consumer lending | Real estate loan | Single-family residential | Criticized (Nonaccrual)
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2022	0	0
2021	0	0
2020	397	1,751
2019	2,024	3,889
2018	3,902	4,295
Prior	8,965	4,231
Revolving Loans	0	0
Revolving Loans Converted to Term Loans	0	0
Total	15,288	14,166
Consumer lending | HELOCs
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2022	0	648
2021	1,963	3,277
2020	3,756	4,696
2019	1,810	1,535
2018	1,649	6,811
Prior	14,682	12,559
Revolving Loans	2,063,193	1,913,485
Revolving Loans Converted to Term Loans	179,581	201,810
Total	2,266,634	2,144,821
Consumer lending | HELOCs | Pass
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2022	0	648
2021	1,956	3,277
2020	3,756	4,644
2019	1,590	1,347
2018	1,463	3,268
Prior	11,629	11,215
Revolving Loans	2,061,729	1,913,478
Revolving Loans Converted to Term Loans	174,742	197,414
Total	2,256,865	2,135,291
Consumer lending | HELOCs | Criticized (Accrual)
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2022	0	0
2021	0	0
2020	0	0
2019	220	0
2018	0	0
Prior	1	371
Revolving Loans	1,464	7
Revolving Loans Converted to Term Loans	1,272	708
Total	2,957	1,086
Consumer lending | HELOCs | Criticized (Nonaccrual)
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2022	0	0
2021	7	0
2020	0	52
2019	0	188
2018	186	3,543
Prior	3,052	973
Revolving Loans	0	0
Revolving Loans Converted to Term Loans	3,567	3,688
Total	6,812	8,444
Consumer lending | Total residential mortgage
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2022	592,760	2,617,606
2021	2,612,298	2,111,647
2020	2,011,124	1,382,834
2019	1,276,142	1,087,267
2018	1,006,166	776,356
Prior	1,808,799	1,147,518
Revolving Loans	2,063,193	1,913,485
Revolving Loans Converted to Term Loans	179,581	201,810
Total	11,550,063	11,238,523
Consumer lending | Other consumer
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2022	539	16,833
2021	16,190	5,258
2020	5,258	0
2019	0	0
2018	0	1,741
Prior	54,062	52,147
Revolving Loans	51,350	51,533
Revolving Loans Converted to Term Loans	0	0
Total	127,399	127,512
Consumer lending | Other consumer | Pass
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2022	538	16,831
2021	16,190	5,258
2020	5,258	0
2019	0	0
2018	0	1,741
Prior	54,062	52,147
Revolving Loans	51,313	51,481
Revolving Loans Converted to Term Loans	0	0
Total	127,361	127,458
Consumer lending | Other consumer | Criticized (Accrual)
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2022	1	2
2021	0	0
2020	0	0
2019	0	0
2018	0	0
Prior	0	0
Revolving Loans	0	0
Revolving Loans Converted to Term Loans	0	0
Total	1	2
Consumer lending | Other consumer | Criticized (Nonaccrual)
Financing Receivable, Vintage Year/Credit Quality Indicator [Line Items]
2022	0	0
2021	0	0
2020	0	0
2019	0	0
2018	0	0
Prior	0	0
Revolving Loans	37	52
Revolving Loans Converted to Term Loans	0	0
Total	$ 37	$ 52