Loans Held for Sale - Composition of Loans Held for Sale (Detail) - USD ($) $ in Thousands		12 Months Ended
Sep. 30, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Receivables Held-for-sale [Abstract]
Multi-family loans, at lower of cost or fair value		$ 482,873	$ 0
Total commercial loans held for sale		482,873	0
Home equity conversion mortgages, at lower of cost or fair value		1,325	0
Residential mortgage loans, at fair value		2,130	1,507
Total consumer loans held for sale		3,455	1,507
Loans held for sale		486,328	1,507
Transfer of loans held for investment to held for sale	$ 499,800	$ 499,774	$ 0	$ 150,638

Loans Receivable Held-for-sale, Net, Not Part of Disposal Group, Consumer

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- Definition

Loans Receivable Held-for-sale, Net, Not Part of Disposal Group, Consumer, Home Equity Conversion

+ References

No definition available.

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- Definition

Loans Receivable Held-for-sale, Net, Not Part of Disposal Group, Commercial, Real Estate1

+ References

No definition available.

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- Definition

Loans Receivable Held-for-sale, Net, Not Part of Disposal Group, Mortgage1

+ References

No definition available.

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- Definition

MultiFamilyCommercialLoansHeldForSale

+ References

No definition available.

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- Definition

Amount, after allowance for bad debt, of loan receivables held-for-sale that are not part of a disposal group. Excludes loans and leases covered under loss sharing agreements and loans classified as debt securities.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=118952595&loc=d3e4428-111522

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- References

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- Definition

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

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=98513485&loc=d3e4304-108586

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=98513485&loc=d3e4332-108586

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=98513485&loc=d3e4313-108586

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