Loans Receivable and Allowance for Credit Losses (Loan Purchases, Sales and Transfers) (Details) - USD ($)	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020
Loans Receivable and Allowance for Credit Losses
Loans transferred from held-for-investment to held-for-sale	$ 145,872,000	$ 110,223,000
Sales	153,417,000	114,865,000
Purchases	310,848,000	133,180,000
Allowance for loan and lease losses, Loans transferred from held-for-investment to held-for-sales, write-offs	39,000	0
Net gains on sales of loans	1,781,000	950,000
Commercial and industrial (“C&I”) \| Originated
Loans Receivable and Allowance for Credit Losses
Sales	131,000,000.0	114,900,000
Loans sold in secondary market \| Purchased
Loans Receivable and Allowance for Credit Losses
Sales	22,400,000	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	125,840,000	102,973,000
Sales	125,879,000	102,973,000
Purchases	178,678,000	130,583,000
Commercial lending \| Commercial real estate (“CRE”)
Loans Receivable and Allowance for Credit Losses
Loans transferred from held-for-investment to held-for-sale	20,032,000	7,250,000
Sales	20,032,000	7,250,000
Purchases	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
Sales	0	0
Purchases	370,000	1,513,000
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
Sales	7,506,000	4,642,000
Purchases	$ 131,800,000	$ 1,084,000

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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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- Definition

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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