Loans Receivable and Allowance for Credit Losses (Loan Purchases, Sales and Transfers) (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Loans Receivable and Allowance for Credit Losses
Loans transferred from held-for-investment to held-for-sale	$ 101,764	$ 33,060	$ 247,636	$ 143,283
Sales	104,180	46,768	257,597	161,633
Purchases	231,578	12,510	542,426	145,690
Allowance for loan and lease losses, Loans transferred from held-for-investment to held-for-sales, write-offs	1,300	0	1,300	0
Net gains on sales of loans	1,491	132	3,272	1,082
Commercial and industrial (“C&I”) \| Originated
Loans Receivable and Allowance for Credit Losses
Sales	67,600		198,600
Commercial and industrial (“C&I”) \| Single-family residential \| Originated
Loans Receivable and Allowance for Credit Losses
Sales		46,800		161,600
Loans sold in secondary market \| Purchased
Loans Receivable and Allowance for Credit Losses
Sales	36,600	0	59,000	0
Commercial lending \| Commercial and industrial (“C&I”)
Loans Receivable and Allowance for Credit Losses
Loans transferred from held-for-investment to held-for-sale	84,745	33,060	210,585	136,033
Sales	84,503	33,060	210,382	136,033
Purchases	66,415	12,503	245,093	143,086
Commercial lending \| Commercial real estate (“CRE”)
Loans Receivable and Allowance for Credit Losses
Loans transferred from held-for-investment to held-for-sale	17,019		37,051	7,250
Sales	17,019		37,051	7,250
Purchases	0		0	0
Commercial lending \| Real estate loan \| Multifamily residential
Loans Receivable and Allowance for Credit Losses
Loans transferred from held-for-investment to held-for-sale		0	0	0
Sales		0	0	0
Purchases		7	370	1,520
Consumer lending \| Real estate loan \| Single-family residential
Loans Receivable and Allowance for Credit Losses
Loans transferred from held-for-investment to held-for-sale	0	0	0	0
Sales	2,658	13,708	10,164	18,350
Purchases	$ 165,163	$ 0	$ 296,963	$ 1,084

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Amount of loans and leases that have been written off from both loan receivables and allowance reserve for credit loss.

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Amount of increase from purchase of financing receivable.

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Amount of decrease from sale and reclassification to held-for-sale of financing receivable.

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Amount of expense reversal of allowance for credit loss on financing receivable transferred to held-for-sale classification.

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The net gain (loss) resulting from a sale of loans, including adjustments to record loans classified as held-for-sale at the lower-of-cost-or-market and fair value adjustments to loan held for investment purposes.

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