Loans Receivable and Allowance for Credit Losses (Loan Purchases, Sales and Transfers) (Details) - USD ($)	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Loans Receivable and Allowance for Credit Losses
Loans transferred from held-for-investment to held-for-sale	$ 92,228,000	$ 155,767,000
Sales	94,743,000	114,287,000
Purchases	147,814,000	80,046,000
Write-down of loans transferred from loans held-for-investment to loans held-for-sale recorded to allowance for loan losses	73,000	85,000
Net gains from sales of loans held-for-sale during the period, excluding lower of cost or fair value adjustment	915,000	1,600,000
Loans held-for-sale
Loans Receivable and Allowance for Credit Losses
Lower of cost or fair value adjustment	0	0
Commercial and industrial and commercial real estate \| Originated
Loans Receivable and Allowance for Credit Losses
Sales	76,500,000	89,700,000
Loans sold in secondary market \| Purchased
Loans Receivable and Allowance for Credit Losses
Sales	18,200,000	24,600,000
Commercial lending \| Commercial and industrial (“C&I”)
Loans Receivable and Allowance for Credit Losses
Loans transferred from held-for-investment to held-for-sale	75,573,000	146,391,000
Sales	75,646,000	102,365,000
Purchases	107,194,000	64,747,000
Commercial lending \| Commercial real estate (“CRE”)
Loans Receivable and Allowance for Credit Losses
Loans transferred from held-for-investment to held-for-sale	16,655,000	9,376,000
Sales	16,655,000	9,376,000
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	4,218,000	186,000
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	2,442,000	2,546,000
Purchases	$ 36,402,000	$ 15,113,000

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

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
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Amount of addition (reduction) to the amount at which an asset could be incurred (settled) in a current transaction between willing parties.

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The amount of any significant purchases of financing receivables during the reporting period.

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The amount of any significant sales of financing receivables during the reporting period.

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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.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
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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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