Mortgage Banking Operations - Revenue from Mortgage Servicing (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Mortgage Loans on Real Estate [Line Items]
Servicing fees and other	$ 18,385	$ 15,977	$ 36,836	$ 32,156
Changes in fair value of single family MSRs due to modeled amortization	(9,400)	(8,909)	(18,270)	(17,429)
Amortization of multifamily and SBA MSRs	(1,064)	(761)	(2,113)	(1,692)
Net servicing income	7,921	6,307	16,453	13,035
Changes in fair value due to changes in model inputs and/or assumptions	11,299	(6,417)	41,318	(4,285)
Mortgage servicing rights, risk management	(889)	2,457	(1,847)	4,968
Loan servicing income	7,032	8,764	14,606	18,003
Single family [Member]
Mortgage Loans on Real Estate [Line Items]
Changes in fair value of single family MSRs due to modeled amortization	9,400	8,909	18,270	17,429
Changes in fair value due to changes in model inputs and/or assumptions	11,299	(6,426)	41,318	(4,294)
Single family MSRs [Member]
Mortgage Loans on Real Estate [Line Items]
Changes in fair value due to changes in model inputs and/or assumptions	573
Servicing contracts [Member]
Mortgage Loans on Real Estate [Line Items]
Net (loss) gain from derivatives economically hedging MSR	$ (12,188)	$ 8,874	$ (43,165)	$ 9,253

Changes in the fair value of mortgage servicing rights due to modeled amortization.

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- Definition

Changes in MSR fair value due to changes in model inputs and assumptions, net of risk management derivatives.

+ References

No definition available.

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- Definition

Servicing and other related fees, net of payments.

+ References

No definition available.

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- Definition

Servicing fees and other.

+ References

No definition available.

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- Definition

The periodic amortization (in proportion to and over the period of estimated net servicing income or loss) of capitalized servicing rights, which contractually entitle the servicer to receive fees and ancillary revenues for performing billing, collection, disbursement and recordkeeping services in connection with a mortgage portfolio. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 50
-Section 50
-Paragraph 4
-Subparagraph (a)(4)
-URI http://asc.fasb.org/extlink&oid=68078379&loc=d3e122739-111746

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3602-108585

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- Definition

Amount of increase (decrease) in the fair value of derivatives recognized in the income statement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4A
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5618551-113959

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-Subparagraph (a),(c),(d),(e)
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5624171-113959

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

Amount of increase (decrease) from changes in fair value classified as other for a contract to service financial assets under which the benefits of servicing are expected to more than adequately compensate the servicer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 50
-Section 50
-Paragraph 3
-Subparagraph (a)(4)(ii)
-URI http://asc.fasb.org/extlink&oid=68078379&loc=d3e122625-111746

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- Definition

Amount of revenue from servicing real estate mortgages, credit cards, and other financial assets held by others. Includes premiums received in lieu of regular servicing fees.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 225
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04.13 (d))
-URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882

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