Secured Debt Agreements, Net - Credit Facilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Line of Credit Facility [Line Items]
Potential	$ 10,310,189	$ 1,839,698
Repurchase Borrowings Outstanding	9,753,059	1,839,698
Available	557,130	339,428
Collateral Assets	13,157,700	11,729,560
Credit Facilities [Member]
Line of Credit Facility [Line Items]
Potential	10,310,189	9,210,325
Repurchase Borrowings Outstanding	9,753,059	8,870,897
Deutsche Bank [Member]
Line of Credit Facility [Line Items]
Repurchase Borrowings Outstanding	951,600
Deutsche Bank [Member] \| Credit Facilities [Member]
Line of Credit Facility [Line Items]
Potential	2,037,795
Repurchase Borrowings Outstanding	1,971,860
Available	65,935
Collateral Assets	2,573,447	2,325,047
Wells Fargo [Member]
Line of Credit Facility [Line Items]
Repurchase Borrowings Outstanding	148,300	197,700
Wells Fargo [Member] \| Credit Facilities [Member]
Line of Credit Facility [Line Items]
Potential	2,056,769	1,908,509
Repurchase Borrowings Outstanding	2,018,057	1,822,154
Available	38,712	86,355
Collateral Assets	2,621,806	2,514,513
Barclays [Member] \| Credit Facilities [Member]
Line of Credit Facility [Line Items]
Potential	1,629,551	890,620
Repurchase Borrowings Outstanding	1,442,083	890,620
Available	187,468
Collateral Assets	2,044,654	1,113,275
Citibank [Member] \| Credit Facilities [Member]
Line of Credit Facility [Line Items]
Potential	1,159,888	852,470
Repurchase Borrowings Outstanding	1,109,837	663,917
Available	50,051	188,553
Collateral Assets	1,473,745	1,076,085
JP Morgan [Member] \| Credit Facilities [Member]
Line of Credit Facility [Line Items]
Potential	303,288	1,010,628
Repurchase Borrowings Outstanding	259,062	1,010,628
Available	44,226
Collateral Assets	386,545	1,266,259
Bank of America [Member] \| Credit Facilities [Member]
Line of Credit Facility [Line Items]
Potential	603,660	873,446
Repurchase Borrowings Outstanding	513,660	873,446
Available	90,000
Collateral Assets	775,678	1,090,117
Morgan Stanley [Member] \| Credit Facilities [Member]
Line of Credit Facility [Line Items]
Potential	524,162	341,241
Repurchase Borrowings Outstanding	468,048	276,721
Available	56,114	64,520
Collateral Assets	706,080	457,496
Societe Generale [Member] \| Credit Facilities [Member]
Line of Credit Facility [Line Items]
Potential	333,473	321,182
Repurchase Borrowings Outstanding	333,473	321,182
Collateral Assets	437,130	404,048
Goldman Sachs [Member] \| Credit Facilities [Member]
Line of Credit Facility [Line Items]
Potential	474,338	230,140
Repurchase Borrowings Outstanding	450,000	230,140
Available	24,338
Collateral Assets	632,013	295,368
MetLife [Member] \| Credit Facilities [Member]
Line of Credit Facility [Line Items]
Potential	417,677	675,329
Repurchase Borrowings Outstanding	417,677	675,329
Collateral Assets	536,553	852,733
Goldman Sachs - Multi. JV [Member] \| Credit Facilities [Member]
Line of Credit Facility [Line Items]
Potential	203,846	170,060
Repurchase Borrowings Outstanding	203,846	170,060
Collateral Assets	261,461	212,983
Santander [Member] \| Credit Facilities [Member]
Line of Credit Facility [Line Items]
Potential	239,332
Repurchase Borrowings Outstanding	239,332
Collateral Assets	299,597
US Bank - Multi. JV [Member] \| Credit Facilities [Member]
Line of Credit Facility [Line Items]
Potential	279,838
Repurchase Borrowings Outstanding	279,552
Available	286
Collateral Assets	350,034
Bank of America - Multi. JV [Member] \| Credit Facilities [Member]
Line of Credit Facility [Line Items]
Potential	46,572	97,002
Repurchase Borrowings Outstanding	46,572	97,002
Collateral Assets	$ 58,957	$ 121,636

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

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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