Variable Interest Entities - Additional Information (Detail)	1 Months Ended			6 Months Ended
	Feb. 29, 2016 USD ($) Loan	Apr. 30, 2015 USD ($) Loan	Feb. 28, 2015 USD ($) Loan	Jun. 30, 2017 USD ($)		Dec. 31, 2016 USD ($)	[2]	Jun. 30, 2016 USD ($)
Variable Interest Entity [Line Items]
Payments to purchase mortgage loans				$ 49,599,000
Exposure to obligations of VIEs				1,100,000,000
Gain (Loss) recognized upon initial consolidation				0
Other secured financings				$ 3,785,543,000	[1]	$ 3,884,708,000
Pingora
Variable Interest Entity [Line Items]
Variable interest entity, ownership percentage				100.00%
Freddie Mac | Floating Rate Multifamily Mortgage Loans | FREMF 2015-KLSF
Variable Interest Entity [Line Items]
Number of loans in the underlying portfolio | Loan			11
Face value			$ 1,400,000,000
Freddie Mac | Floating Rate Multifamily Mortgage Loans | FREMF 2016-KLH1
Variable Interest Entity [Line Items]
Number of loans in the underlying portfolio | Loan	28
Face value	$ 1,500,000,000
Freddie Mac | Floating Rate Multifamily Mortgage Loans | FREMF 2015-KF07
Variable Interest Entity [Line Items]
Number of loans in the underlying portfolio | Loan		40
Face value		$ 1,200,000,000
Consolidated VIEs | FREMF Trusts
Variable Interest Entity [Line Items]
Exposure to obligations of VIEs				$ 267,200,000
Gain (Loss) recognized upon initial consolidation				0
Debt issue costs expensed				800,000
Mortgage loans, unpaid principal balance				3,600,000,000
Loans 90 days or more past due or on nonaccrual status				0
Gain (Loss) attributable to instrument- specific credit risk				0
Consolidated VIEs | Residential Mortgage Loan Trust
Variable Interest Entity [Line Items]
Mortgage loans, unpaid principal balance				147,900,000
Consolidated VIEs | Borrower
Variable Interest Entity [Line Items]
Credit facility, maximum borrowing capacity								$ 300,000,000
Other secured financings				189,600,000
Consolidated VIEs | Borrower | Consolidation, Eliminations
Variable Interest Entity [Line Items]
Intercompany receivable				189,600,000
Consolidated VIEs | Corporate Debt Securities | Borrower
Variable Interest Entity [Line Items]
Transferred loans pledged as collateral for credit facility				437,800,000
Consolidated VIEs | Freddie Mac | FREMF 2015-KLSF
Variable Interest Entity [Line Items]
Variable interest entity, consolidated, carrying amount, assets				1,300,000,000
Variable interest entity, consolidated, carrying amount, liabilities				1,200,000,000
Payments to purchase mortgage loans			$ 102,100,000
Consolidated VIEs | Freddie Mac | FREMF 2016-KLH1
Variable Interest Entity [Line Items]
Face value	112,000,000
Variable interest entity, consolidated, carrying amount, assets				1,500,000,000
Variable interest entity, consolidated, carrying amount, liabilities				1,400,000,000
Payments to purchase mortgage loans	107,600,000
Discounted value	$ 4,400,000
Consolidated VIEs | Freddie Mac | FREMF 2015-KF07
Variable Interest Entity [Line Items]
Variable interest entity, consolidated, carrying amount, assets				800,000,000
Variable interest entity, consolidated, carrying amount, liabilities				$ 800,000,000
Payments to purchase mortgage loans		$ 89,400,000

[1] As a result of a change to a clearing organization's rulebook effective January 3, 2017, beginning with the first quarter 2017 and in subsequent periods the Company is presenting the fair value of centrally cleared interest rate swaps net of variation margin pledged under such transactions. The variation margin was previously reported under cash and cash equivalents and is currently reported as a reduction to interest rate swaps, at fair value. Balances reported prior to the effective date balances will not be adjusted.

[2] Derived from the audited consolidated financial statements at December 31, 2016.