Loans Receivable and Allowance for Credit Losses (Composition of Loans Held-for-Investment) (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
LOANS RECEIVABLE AND ALLOWANCE FOR LOAN LOSSES
Loans held-for-investment	$ 41,693,781	$ 38,390,955
Allowance for loan losses	(541,579)	(619,983)
Loans held-for-investment, net	41,152,202	37,770,972
Deferred loan fees, unearned fees, unamortized premiums and unaccreted discounts	(50,700)	(58,800)
CARES Act, Paycheck Protection Program
LOANS RECEIVABLE AND ALLOWANCE FOR LOAN LOSSES
Net origination fees	(5,700)	(12,700)
C&I \| CARES Act, Paycheck Protection Program
LOANS RECEIVABLE AND ALLOWANCE FOR LOAN LOSSES
Loans held-for-investment	534,200	1,570,000
Commercial Lending
LOANS RECEIVABLE AND ALLOWANCE FOR LOAN LOSSES
Loans held-for-investment	30,327,746	28,440,027
Commercial Lending \| C&I
LOANS RECEIVABLE AND ALLOWANCE FOR LOAN LOSSES
Loans held-for-investment	14,150,608	13,631,726
Commercial Lending \| CRE
LOANS RECEIVABLE AND ALLOWANCE FOR LOAN LOSSES
Loans held-for-investment	12,155,047	11,174,611
Commercial Lending \| Residential loan \| Multifamily
LOANS RECEIVABLE AND ALLOWANCE FOR LOAN LOSSES
Loans held-for-investment	3,675,605	3,033,998
Commercial Lending \| Construction and land
LOANS RECEIVABLE AND ALLOWANCE FOR LOAN LOSSES
Loans held-for-investment	346,486	599,692
Commercial Lending \| Total CRE
LOANS RECEIVABLE AND ALLOWANCE FOR LOAN LOSSES
Loans held-for-investment	16,177,138	14,808,301
Consumer Lending
LOANS RECEIVABLE AND ALLOWANCE FOR LOAN LOSSES
Loans held-for-investment	11,366,035	9,950,928
Consumer Lending \| Residential loan \| Single-family
LOANS RECEIVABLE AND ALLOWANCE FOR LOAN LOSSES
Loans held-for-investment	9,093,702	8,185,953
Consumer Lending \| HELOCs
LOANS RECEIVABLE AND ALLOWANCE FOR LOAN LOSSES
Loans held-for-investment	2,144,821	1,601,716
Consumer Lending \| Total residential mortgage
LOANS RECEIVABLE AND ALLOWANCE FOR LOAN LOSSES
Loans held-for-investment	11,238,523	9,787,669
Consumer Lending \| Other consumer
LOANS RECEIVABLE AND ALLOWANCE FOR LOAN LOSSES
Loans held-for-investment	$ 127,512	$ 163,259

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Amount of allowance for credit loss on financing receivable. Excludes allowance for financing receivable covered under loss sharing agreement.

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Amount excluding accrued interest, before allowance for credit loss, of financing receivable.

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Amount, after allowance for credit loss, of financing receivable. Excludes financing receivable covered under loss sharing agreement.

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