Loans Receivable and Allowance for Credit Losses (Loan Purchases, Sales and Transfers) (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Loans Receivable and Allowance for Credit Losses
Loans transferred from held-for-investment to held-for-sale	$ 129,864	$ 65,953	$ 285,631	$ 343,977
Sales	178,916	88,760	293,203	364,705
Purchases	309,776	221,454	389,822	368,696
Write-down of loans transferred from loans held-for-investment to loans held-for-sale recorded to allowance for loan losses	13,300	117	13,400	209
Net gains from sales of loans held-for-sale during the period, excluding lower of cost or fair value adjustment	2,300	1,600	3,900	4,400
Lower of cost or fair value adjustment		(8)		61
C & I and CRE \| Originated
Loans Receivable and Allowance for Credit Losses
Sales	103,500	38,300	193,200	67,600
Loans sold in secondary market \| Purchased
Loans Receivable and Allowance for Credit Losses
Sales	75,400	50,500	100,000	297,100
Commercial lending \| Commercial and industrial (“C&I”)
Loans Receivable and Allowance for Credit Losses
Loans transferred from held-for-investment to held-for-sale	99,449	58,817	245,840	324,076
Sales	140,326	76,441	242,691	313,120
Purchases	285,615	220,612	350,362	367,728
Commercial lending \| Commercial real estate (“CRE”)
Loans Receivable and Allowance for Credit Losses
Loans transferred from held-for-investment to held-for-sale	30,415	5,668	39,791	18,433
Sales	30,415	5,668	39,791	18,433
Purchases	0	0	0	0
Commercial lending \| Real estate loan \| Multifamily
Loans Receivable and Allowance for Credit Losses
Loans transferred from held-for-investment to held-for-sale	0	532	0	532
Sales	0	532	0	532
Purchases	3,249	714	3,435	840
Commercial lending \| Construction and land
Loans Receivable and Allowance for Credit Losses
Loans transferred from held-for-investment to held-for-sale	0	687	0	687
Sales	0	687	0	687
Purchases	0	0	0	0
Consumer lending \| Real estate loan \| Single-family
Loans Receivable and Allowance for Credit Losses
Loans transferred from held-for-investment to held-for-sale	0	249	0	249
Sales	8,175	5,432	10,721	9,742
Purchases	20,912	128	36,025	128
Consumer lending \| Other consumer
Loans Receivable and Allowance for Credit Losses
Loans transferred from held-for-investment to held-for-sale	0	0	0	0
Sales	0	0	0	22,191
Purchases	$ 0	$ 0	$ 0	$ 0

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

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (c)(3)
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953423-111524

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.7(d))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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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 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/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 24
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3521-108585

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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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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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