Debt Securities Abstract [Abstract]

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Financial assets, fair value disclosure.

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- Definition

Mortgage loans fair value disclosure.

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Mortgaged Loans, Far Value Disclosure [Abstract]

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- Definition

Other derivative instrument obligations meeting the definition of an asset which the Company is a party to as of the balance sheet date.

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This element represents the fair value of derivative liabilities categorized as other as of the balance sheet date.

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- Definition

Securitized debt of consolidated VIEs fair value disclosure.

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The fair value as of the balance sheet date of financial instruments and other positions owned by the entity and pledged to counterparties as collateral, including: (1) mortgages, mortgage-backed and asset backed securities; (2) US government and agency obligations; (3) state and municipal government obligations; (4) other sovereign government debt; (5) corporate obligations; (6) corporate equities; (7) principal investments; (8) derivative contracts; and (9) physical commodities.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 30
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=66007379&loc=d3e113888-111728

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 30
-Section 50
-Paragraph 1A
-Subparagraph (c)(2)
-URI http://asc.fasb.org/extlink&oid=64858031&loc=SL6224234-111729

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The fair value as of the balance sheet date of firm holdings in mortgages, mortgage backed securities (investment instruments that represent ownership of an undivided interest in a group of mortgages, where principal and interest from the individual mortgages are used to pay investors' principal and interest on the mortgage backed security) and asset-backed securities that are primarily paid from the cash flows of a discrete pool of receivables or other financial assets (such as credit-card receivables), either fixed or revolving, that by their terms convert into cash within a finite time period. Includes both pledged (to counterparties as collateral for financing transactions) and unpledged holdings.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 940
-SubTopic 320
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=35711157&loc=d3e42546-110969

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Fair value of firm holdings in securities classified as other. Includes pledged and unpledged holdings.

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Fair value of financial obligations, including, but not limited to, debt instruments, derivative liabilities, federal funds purchased and sold under agreements to repurchase, securities loaned or sold under agreements to repurchase, financial instruments sold not yet purchased, guarantees, line of credit, loans and notes payable, servicing liability, and trading liabilities.

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Fair value as of the balance sheet date of interest rate derivative assets, which includes all such derivative instruments in hedging and nonhedging relationships that are recognized as assets.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 10
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=77997519&loc=d3e13433-108611

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Fair value as of the balance sheet date of interest rate derivative liabilities, which includes all such derivative instruments in hedging and nonhedging relationships that are recognized as liabilities.

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Fair value of securitized, pay-through debt securities collateralized by real estate mortgage loans classified as available-for-sale.

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Fair value of an asset representing net future revenue from contractually specified servicing fees, late charges, and other ancillary revenues, in excess of future costs related to servicing arrangements.

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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)(1)
-URI http://asc.fasb.org/extlink&oid=68078379&loc=d3e122625-111746

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FAIR VALUE MEASUREMENTS - Estimated Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Jun. 30, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Dec. 31, 2016
Securities
Mortgage-backed securities	$ 91,338,611		$ 92,563,572
Loans
Mortgage servicing rights	588,833	$ 599,014	580,860	$ 570,218	$ 605,653	$ 652,216
Assets transferred or pledged to securitization vehicles	4,287,821		3,306,133
Derivative assets
Interest rate swaps	97,002		30,272
Derivative liabilities
Interest rate swaps	311,729		569,129
Residential mortgage loans
Loans
Loans	1,983,015		1,438,322
Fair Value, Measurements, Recurring
Securities
Agency mortgage-backed securities	89,290,128		90,551,763
Credit risk transfer securities	688,521		651,764
Loans
Mortgage servicing rights	588,833		580,860
Assets transferred or pledged to securitization vehicles	4,287,821		3,306,133
Derivative assets
Interest rate swaps	97,002		30,272
Other derivatives	307,839		283,613
Total assets	97,837,245		97,722,996
Liabilities:
Debt issued by securitization vehicles	3,799,542		2,971,771
Derivative liabilities
Interest rate swaps	311,729		569,129
Other derivatives	68,065		38,725
Total liabilities	4,179,336		3,579,625
Fair Value, Measurements, Recurring \| Commercial Securities
Securities
Mortgage-backed securities	186,495		262,751
Fair Value, Measurements, Recurring \| Residential mortgage loans
Loans
Loans	1,217,139		958,546
Fair Value, Measurements, Recurring \| Non-Agency Mortgage-backed Securities
Securities
Mortgage-backed securities	1,173,467		1,097,294
Fair Value, Measurements, Recurring \| Level 1
Securities
Agency mortgage-backed securities	0		0
Credit risk transfer securities	0		0
Loans
Mortgage servicing rights	0		0
Assets transferred or pledged to securitization vehicles	0		0
Derivative assets
Interest rate swaps	0		0
Other derivatives	221,516		218,361
Total assets	221,516		218,361
Liabilities:
Debt issued by securitization vehicles	0		0
Derivative liabilities
Interest rate swaps	0		0
Other derivatives	482		12,285
Total liabilities	482		12,285
Fair Value, Measurements, Recurring \| Level 1 \| Commercial Securities
Securities
Mortgage-backed securities	0		0
Fair Value, Measurements, Recurring \| Level 1 \| Residential mortgage loans
Loans
Loans	0		0
Fair Value, Measurements, Recurring \| Level 1 \| Non-Agency Mortgage-backed Securities
Securities
Mortgage-backed securities	0		0
Fair Value, Measurements, Recurring \| Level 2
Securities
Agency mortgage-backed securities	89,290,128		90,551,763
Credit risk transfer securities	688,521		651,764
Loans
Mortgage servicing rights	0		0
Assets transferred or pledged to securitization vehicles	4,287,821		3,306,133
Derivative assets
Interest rate swaps	97,002		30,272
Other derivatives	86,323		65,252
Total assets	97,026,896		96,923,775
Liabilities:
Debt issued by securitization vehicles	3,799,542		2,971,771
Derivative liabilities
Interest rate swaps	311,729		569,129
Other derivatives	67,583		26,440
Total liabilities	4,178,854		3,567,340
Fair Value, Measurements, Recurring \| Level 2 \| Commercial Securities
Securities
Mortgage-backed securities	186,495		262,751
Fair Value, Measurements, Recurring \| Level 2 \| Residential mortgage loans
Loans
Loans	1,217,139		958,546
Fair Value, Measurements, Recurring \| Level 2 \| Non-Agency Mortgage-backed Securities
Securities
Mortgage-backed securities	1,173,467		1,097,294
Fair Value, Measurements, Recurring \| Level 3
Securities
Agency mortgage-backed securities	0		0
Credit risk transfer securities	0		0
Loans
Mortgage servicing rights	588,833		580,860
Assets transferred or pledged to securitization vehicles	0		0
Derivative assets
Interest rate swaps	0		0
Other derivatives	0		0
Total assets	588,833		580,860
Liabilities:
Debt issued by securitization vehicles	0		0
Derivative liabilities
Interest rate swaps	0		0
Other derivatives	0		0
Total liabilities	0		0
Fair Value, Measurements, Recurring \| Level 3 \| Commercial Securities
Securities
Mortgage-backed securities	0		0
Fair Value, Measurements, Recurring \| Level 3 \| Residential mortgage loans
Loans
Loans	0		0
Fair Value, Measurements, Recurring \| Level 3 \| Non-Agency Mortgage-backed Securities
Securities
Mortgage-backed securities	$ 0		$ 0