Transfers of Residential Loans - Summary of Cash Flows Related to Sales of Mortgage Loans (Detail) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Transfers and Servicing [Abstract]
Cash proceeds received from sales, net of fees	$ 4,551,321	$ 4,825,191	$ 9,803,873	$ 10,290,056
Servicing fees collected	29,563	36,407	60,366	71,179
Repurchases of previously sold loans	$ 13,509	$ 10,386	$ 31,012	$ 16,318

Cash Flows between a transferor and a transferee attributable to newly transferred assets related to either a securitization, asset-backed financing arrangement, or similar transfer in which the transferor has continuing involvement with the transferred financial assets underlying the transaction (including, but not limited to, servicing, recourse, and restrictions on transferor's interests in the transferred financial assets).

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (d)(1)
-URI http://asc.fasb.org/extlink&oid=64830801&loc=d3e107207-111719

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- Definition

Cash Flows between a transferor and a transferee attributable to purchases of previously transferred financial assets (or its underlying collateral) related to a securitization, asset-backed financing arrangement, or similar transfer in which the transferor has continuing involvement with the transferred financial assets underlying the transaction (including, but not limited to, servicing, recourse, and restrictions on transferor's interests in the transferred financial assets).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph b
-URI http://asc.fasb.org/extlink&oid=64830801&loc=d3e107207-111719

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- Definition

Cash Flows between a transferee and a transferor attributable to servicing fees related to a securitization, asset-backed financing arrangement, or similar transfer in which the transferor has continuing involvement with the transferred financial assets underlying the transaction (including, but not limited to, servicing, recourse, and restrictions on transferor's interests in the transferred financial assets).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph d
-URI http://asc.fasb.org/extlink&oid=64830801&loc=d3e107207-111719

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Balance Type:	debit
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- References

No definition available.

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