Loans Receivable and Allowance for Credit Losses (Loan Purchases, Sales and Transfers) (Details) - USD ($)	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019
Loans Receivable and Allowance for Credit Losses
Loans transferred from held-for-investment to held-for-sale	$ 110,223,000	$ 92,228,000
Sales	114,865,000	94,743,000
Purchases	133,180,000	147,814,000
Write-down of loans transferred from loans held-for-investment to loans held-for-sale recorded to allowance for loan losses	0	73,000
Net gains from sales of loans held-for-sale during the period	950,000	915,000
Commercial and industrial (“C&I”)
Loans Receivable and Allowance for Credit Losses
Write-down of loans transferred from loans held-for-investment to loans held-for-sale recorded to allowance for loan losses	12,000,000.0
Commercial and industrial (“C&I”) \| Originated
Loans Receivable and Allowance for Credit Losses
Sales	114,900,000	76,500,000
Loans sold in secondary market \| Purchased
Loans Receivable and Allowance for Credit Losses
Sales	0	18,200,000
Commercial lending \| Commercial and industrial (“C&I”)
Loans Receivable and Allowance for Credit Losses
Loans transferred from held-for-investment to held-for-sale	102,973,000	75,573,000
Sales	102,973,000	75,646,000
Purchases	130,583,000	107,194,000
Write-down of loans transferred from loans held-for-investment to loans held-for-sale recorded to allowance for loan losses	11,977,000
Commercial lending \| Commercial real estate (“CRE”)
Loans Receivable and Allowance for Credit Losses
Loans transferred from held-for-investment to held-for-sale	7,250,000	16,655,000
Sales	7,250,000	16,655,000
Purchases	0	0
Write-down of loans transferred from loans held-for-investment to loans held-for-sale recorded to allowance for loan losses	954,000
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	1,513,000	4,218,000
Write-down of loans transferred from loans held-for-investment to loans held-for-sale recorded to allowance for loan losses	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	0	0
Sales	4,642,000	2,442,000
Purchases	1,084,000	$ 36,402,000
Write-down of loans transferred from loans held-for-investment to loans held-for-sale recorded to allowance for loan losses	$ 0

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- Definition

Amount of writeoff of financing receivable, charged against allowance 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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- Definition

The gains (losses) included in earnings that represent the difference between the sale price and the carrying value of loans and leases that were sold during the reporting period. This element refers to the gain (loss) and not to the cash proceeds of the sales. This element is a noncash adjustment to net income when calculating net cash generated by operating activities using the indirect method.

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Value of loans and leases held in the entity's portfolio transferred to loans and leases held-for-sale in noncash transactions.

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