Loans Receivable and Allowance for Credit Losses (Loan Purchases, Sales and Transfers) (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Loans Receivable and Allowance for Credit Losses
Loans transferred from held-for-investment to held-for-sale	$ 163,780	$ 89,394	$ 411,416	$ 253,302
Sales	169,830	124,084	427,427	306,342
Purchases	203,291	18,132	745,717	163,822
Allowance for loan and lease losses, Loans transferred from held-for-investment to held-for-sales, write-offs	3,600	2,800	4,900	2,800
Net gains on sales of loans	3,329	361	6,601	1,443
Commercial and industrial (“C&I”) \| Originated
Loans Receivable and Allowance for Credit Losses
Sales	143,300		341,900
Commercial and industrial (“C&I”) \| Single-family residential \| Originated
Loans Receivable and Allowance for Credit Losses
Sales		112,300		294,600
Loans sold in secondary market \| Purchased
Loans Receivable and Allowance for Credit Losses
Sales	26,500	11,800	85,500	11,800
Commercial lending \| Commercial and industrial (“C&I”)
Loans Receivable and Allowance for Credit Losses
Loans transferred from held-for-investment to held-for-sale	117,196	89,394	327,781	246,052
Sales	118,851	92,237	329,233	248,895
Purchases	65,354	0	310,447	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	24,120		61,171	7,250
Sales	24,120		61,171	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		838	370	2,358
Commercial lending \| Construction and land
Loans Receivable and Allowance for Credit Losses
Loans transferred from held-for-investment to held-for-sale	17,226		17,226
Sales	19,900		19,900
Purchases	0		0
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	5,238	0	5,238	0
Sales	6,959	31,847	17,123	50,197
Purchases	$ 137,937	$ 17,294	$ 434,900	$ 18,378

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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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