Secured Debt Agreements, Net - Credit Facilities (Detail) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Line of Credit Facility [Line Items]
Potential	$ 9,465,742	$ 2,037,795
Repurchase Borrowings Outstanding	9,019,652	1,971,860
Available	446,090	557,130
Collateral Assets	12,158,542	13,157,700
Credit Facilities [Member]
Line of Credit Facility [Line Items]
Potential	9,465,742	10,310,189
Repurchase Borrowings Outstanding	9,019,652	9,753,059
Deutsche Bank [Member]
Line of Credit Facility [Line Items]
Repurchase Borrowings Outstanding	914,200
Deutsche Bank [Member] \| Credit Facilities [Member]
Line of Credit Facility [Line Items]
Potential	1,958,510
Repurchase Borrowings Outstanding	1,870,556
Available	87,954	65,935
Collateral Assets	2,494,270	2,573,447
Barclays [Member] \| Credit Facilities [Member]
Line of Credit Facility [Line Items]
Potential	1,618,795	1,629,551
Repurchase Borrowings Outstanding	1,529,553	1,442,083
Available	89,242	187,468
Collateral Assets	2,023,495	2,044,654
Wells Fargo [Member]
Line of Credit Facility [Line Items]
Repurchase Borrowings Outstanding	146,200	194,900
Wells Fargo [Member] \| Credit Facilities [Member]
Line of Credit Facility [Line Items]
Potential	1,492,906	2,056,769
Repurchase Borrowings Outstanding	1,464,938	2,018,057
Available	27,968	38,712
Collateral Assets	1,928,798	2,621,806
Citibank [Member] \| Credit Facilities [Member]
Line of Credit Facility [Line Items]
Potential	919,790	1,159,888
Repurchase Borrowings Outstanding	875,416	1,109,837
Available	44,374	50,051
Collateral Assets	1,178,568	1,473,745
Goldman Sachs [Member] \| Credit Facilities [Member]
Line of Credit Facility [Line Items]
Potential	555,612	474,338
Repurchase Borrowings Outstanding	555,612	450,000
Available	0	24,338
Collateral Assets	727,728	632,013
Bank of America [Member] \| Credit Facilities [Member]
Line of Credit Facility [Line Items]
Potential	538,473	603,660
Repurchase Borrowings Outstanding	443,473	513,660
Available	95,000	90,000
Collateral Assets	749,127	775,678
Morgan Stanley [Member] \| Credit Facilities [Member]
Line of Credit Facility [Line Items]
Potential	493,208	524,162
Repurchase Borrowings Outstanding	438,202	468,048
Available	55,006	56,114
Collateral Assets	670,544	706,080
MetLife [Member] \| Credit Facilities [Member]
Line of Credit Facility [Line Items]
Potential	434,131	417,677
Repurchase Borrowings Outstanding	434,131	417,677
Available	0
Collateral Assets	545,573	536,553
JP Morgan [Member] \| Credit Facilities [Member]
Line of Credit Facility [Line Items]
Potential	401,865	303,288
Repurchase Borrowings Outstanding	357,639	259,062
Available	44,226	44,226
Collateral Assets	509,766	386,545
US Bank - Multi. JV [Member] \| Credit Facilities [Member]
Line of Credit Facility [Line Items]
Potential	281,872	279,838
Repurchase Borrowings Outstanding	279,552	279,552
Available	2,320	286
Collateral Assets	352,340	350,034
Goldman Sachs - Multi. JV [Member] \| Credit Facilities [Member]
Line of Credit Facility [Line Items]
Potential	240,263	203,846
Repurchase Borrowings Outstanding	240,263	203,846
Available	0
Collateral Assets	306,367	261,461
Societe Generale [Member] \| Credit Facilities [Member]
Line of Credit Facility [Line Items]
Potential	236,698	333,473
Repurchase Borrowings Outstanding	236,698	333,473
Available	0
Collateral Assets	300,386	437,130
Santander [Member] \| Credit Facilities [Member]
Line of Credit Facility [Line Items]
Potential	235,447	239,332
Repurchase Borrowings Outstanding	235,447	239,332
Available	0
Collateral Assets	298,865	299,597
Bank of America - Multi. JV [Member] \| Credit Facilities [Member]
Line of Credit Facility [Line Items]
Potential	58,172	46,572
Repurchase Borrowings Outstanding	58,172	46,572
Available	0
Collateral Assets	$ 72,715	$ 58,957

Amount of assets pledged to secure a debt instrument.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 470
-Section 50
-Paragraph 3
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=75038535&loc=d3e64711-112823

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- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(16))
-URI http://asc.fasb.org/extlink&oid=119400593&loc=d3e572229-122910

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Balance Type:	credit
Period Type:	instant

- Definition

Amount of current borrowing capacity under the credit facility considering any current restrictions on the amount that could be borrowed (for example, borrowings may be limited by the amount of current assets), but without considering any amounts currently outstanding under the facility.

+ References

+ Details

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Balance Type:	credit
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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 borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

+ References

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Balance Type:	credit
Period Type:	instant