Loans Receivable and Allowance for Credit Losses (Composition of Non-PCI and PCI Loans) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
LOANS RECEIVABLE AND ALLOWANCE FOR LOAN LOSSES
Loans held-for-investment	$ 34,778,539	$ 32,385,189
Allowance for loan losses	(358,287)	(311,322)
Loans held-for-investment, net	34,420,252	32,073,867
Commercial Lending
LOANS RECEIVABLE AND ALLOWANCE FOR LOAN LOSSES
Loans held-for-investment	25,914,252	24,326,631
Commercial Lending \| C&I
LOANS RECEIVABLE AND ALLOWANCE FOR LOAN LOSSES
Loans held-for-investment	12,150,931	12,056,970
Commercial Lending \| CRE
LOANS RECEIVABLE AND ALLOWANCE FOR LOAN LOSSES
Loans held-for-investment	10,278,448	9,260,199
Commercial Lending \| Residential loan \| Multifamily
LOANS RECEIVABLE AND ALLOWANCE FOR LOAN LOSSES
Loans held-for-investment	2,856,374	2,470,668
Commercial Lending \| Construction and land
LOANS RECEIVABLE AND ALLOWANCE FOR LOAN LOSSES
Loans held-for-investment	628,499	538,794
Commercial Lending \| Total CRE
LOANS RECEIVABLE AND ALLOWANCE FOR LOAN LOSSES
Loans held-for-investment	13,763,321	12,269,661
Consumer Lending
LOANS RECEIVABLE AND ALLOWANCE FOR LOAN LOSSES
Loans held-for-investment	8,864,287	8,058,558
Consumer Lending \| Residential loan \| Single-family
LOANS RECEIVABLE AND ALLOWANCE FOR LOAN LOSSES
Loans held-for-investment	7,108,590	6,036,454
Consumer Lending \| HELOCs
LOANS RECEIVABLE AND ALLOWANCE FOR LOAN LOSSES
Loans held-for-investment	1,472,783	1,690,834
Consumer Lending \| Total residential mortgage
LOANS RECEIVABLE AND ALLOWANCE FOR LOAN LOSSES
Loans held-for-investment	8,581,373	7,727,288
Consumer Lending \| Other consumer
LOANS RECEIVABLE AND ALLOWANCE FOR LOAN LOSSES
Loans held-for-investment	282,914	331,270
Non-PCI loans
LOANS RECEIVABLE AND ALLOWANCE FOR LOAN LOSSES
Loans held-for-investment	34,555,668	32,077,166
Allowance for loan losses	(358,287)	(311,300)
Loans held-for-investment, net	34,197,381	31,765,866
Deferred loan fees, unearned fees, unamortized premiums and unaccreted discounts	(43,200)	(48,900)
Non-PCI loans \| Commercial Lending
LOANS RECEIVABLE AND ALLOWANCE FOR LOAN LOSSES
Loans held-for-investment	25,777,039	24,124,659
Non-PCI loans \| Commercial Lending \| C&I
LOANS RECEIVABLE AND ALLOWANCE FOR LOAN LOSSES
Loans held-for-investment	12,149,121	12,054,818
Non-PCI loans \| Commercial Lending \| CRE
LOANS RECEIVABLE AND ALLOWANCE FOR LOAN LOSSES
Loans held-for-investment	10,165,247	9,097,165
Non-PCI loans \| Commercial Lending \| Residential loan \| Multifamily
LOANS RECEIVABLE AND ALLOWANCE FOR LOAN LOSSES
Loans held-for-investment	2,834,212	2,433,924
Non-PCI loans \| Commercial Lending \| Construction and land
LOANS RECEIVABLE AND ALLOWANCE FOR LOAN LOSSES
Loans held-for-investment	628,459	538,752
Non-PCI loans \| Commercial Lending \| Total CRE
LOANS RECEIVABLE AND ALLOWANCE FOR LOAN LOSSES
Loans held-for-investment	13,627,918	12,069,841
Non-PCI loans \| Consumer Lending
LOANS RECEIVABLE AND ALLOWANCE FOR LOAN LOSSES
Loans held-for-investment	8,778,629	7,952,507
Non-PCI loans \| Consumer Lending \| Residential loan \| Single-family
LOANS RECEIVABLE AND ALLOWANCE FOR LOAN LOSSES
Loans held-for-investment	7,028,979	5,939,258
Non-PCI loans \| Consumer Lending \| HELOCs
LOANS RECEIVABLE AND ALLOWANCE FOR LOAN LOSSES
Loans held-for-investment	1,466,736	1,681,979
Non-PCI loans \| Consumer Lending \| Total residential mortgage
LOANS RECEIVABLE AND ALLOWANCE FOR LOAN LOSSES
Loans held-for-investment	8,495,715	7,621,237
Non-PCI loans \| Consumer Lending \| Other consumer
LOANS RECEIVABLE AND ALLOWANCE FOR LOAN LOSSES
Loans held-for-investment	282,914	331,270
PCI Loans
LOANS RECEIVABLE AND ALLOWANCE FOR LOAN LOSSES
Loans held-for-investment	222,871	308,023
Allowance for loan losses	0	(22)
Loans held-for-investment, net	222,871	308,001
Discount related to ASC 310-30	14,300	22,200
PCI Loans \| Commercial Lending
LOANS RECEIVABLE AND ALLOWANCE FOR LOAN LOSSES
Loans held-for-investment	137,213	201,972
PCI Loans \| Commercial Lending \| C&I
LOANS RECEIVABLE AND ALLOWANCE FOR LOAN LOSSES
Loans held-for-investment	1,810	2,152
PCI Loans \| Commercial Lending \| CRE
LOANS RECEIVABLE AND ALLOWANCE FOR LOAN LOSSES
Loans held-for-investment	113,201	163,034
PCI Loans \| Commercial Lending \| Residential loan \| Multifamily
LOANS RECEIVABLE AND ALLOWANCE FOR LOAN LOSSES
Loans held-for-investment	22,162	36,744
PCI Loans \| Commercial Lending \| Construction and land
LOANS RECEIVABLE AND ALLOWANCE FOR LOAN LOSSES
Loans held-for-investment	40	42
PCI Loans \| Commercial Lending \| Total CRE
LOANS RECEIVABLE AND ALLOWANCE FOR LOAN LOSSES
Loans held-for-investment	135,403	199,820
PCI Loans \| Consumer Lending
LOANS RECEIVABLE AND ALLOWANCE FOR LOAN LOSSES
Loans held-for-investment	85,658	106,051
PCI Loans \| Consumer Lending \| Residential loan \| Single-family
LOANS RECEIVABLE AND ALLOWANCE FOR LOAN LOSSES
Loans held-for-investment	79,611	97,196
PCI Loans \| Consumer Lending \| HELOCs
LOANS RECEIVABLE AND ALLOWANCE FOR LOAN LOSSES
Loans held-for-investment	6,047	8,855
PCI Loans \| Consumer Lending \| Total residential mortgage
LOANS RECEIVABLE AND ALLOWANCE FOR LOAN LOSSES
Loans held-for-investment	85,658	106,051
PCI Loans \| Consumer Lending \| Other consumer
LOANS RECEIVABLE AND ALLOWANCE FOR LOAN LOSSES
Loans held-for-investment	$ 0	$ 0

Financing Receivable, Discount

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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 after allowance and deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements and loans held for sale.

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Amount, before allowance for credit loss, of financing receivable.

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