Organization and Operations (Details)	Jun. 28, 2017 shares
Organization and Operations [Abstract]
Shares of Granite Point Mortgage Trust Inc. common stock received in exchange for contribution (in shares)	33,100,000
Ownership percentage in Granite Point Mortgage Trust Inc.	76.50%

Balance held at close of period in number of shares.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 946
-SubTopic 210
-Section 50
-Paragraph 6
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=99383244&loc=d3e12121-115841

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 946
-SubTopic 320
-Section S99
-Paragraph 6
-Subparagraph (SX 210.12-14.Column B)
-URI http://asc.fasb.org/extlink&oid=50485924&loc=d3e611322-123010

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 946
-SubTopic 320
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-URI http://asc.fasb.org/extlink&oid=50485924&loc=d3e611225-123010

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 946
-SubTopic 320
-Section S99
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-URI http://asc.fasb.org/extlink&oid=50485924&loc=d3e611133-123010

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Balance Type:	na
Period Type:	instant