Investments in Unconsolidated Ventures (Details) (USD $)	3 Months Ended		6 Months Ended					3 Months Ended			6 Months Ended				1 Months Ended						3 Months Ended		6 Months Ended								3 Months Ended	6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013	Apr. 30, 2013	Apr. 30, 2013 Sponsor	Jun. 30, 2014 PE Investment I joint_venture	Mar. 31, 2014 PE Investment I	Jun. 30, 2013 PE Investment I	Jun. 30, 2014 PE Investment I joint_venture	Jun. 30, 2013 PE Investment I	Dec. 31, 2013 PE Investment I	Feb. 28, 2013 PE Investment I fund	Feb. 28, 2013 PE Investment I NorthStar Real Estate Income Trust Inc Cash distribution until NorthStar Entities receive a 1.5x multiple on all of their invested capital	Feb. 28, 2013 PE Investment I NorthStar Real Estate Income Trust Inc Remaining cash distribution	Feb. 28, 2013 PE Investment I Class B Partner Cash Distributions To Prior Owner Of Funds Interests Until NorthStar Receipt Of One And Half Of Invested Capital	Feb. 28, 2013 PE Investment I Class B Partner Cash Distributions to Prior Owner of Funds Interests Until Receipt of Remaining Capital after 30 June 2012	Feb. 28, 2013 PE Investment I Class B Partner Remaining cash distribution	Feb. 28, 2013 PE Investment I Sponsor	Jun. 30, 2014 PE Investment II	Mar. 31, 2014 PE Investment II	Jun. 30, 2014 PE Investment II	Dec. 31, 2013 PE Investment II	Jun. 30, 2014 PE Investment II Sponsor property	Sep. 30, 2012 PE Investment II Sponsor	Jun. 30, 2014 PE Investment II Vintage Funds	Apr. 30, 2013 Registrant and Sponsor Milford Plaza hotel	Jun. 30, 2014 Mezzanine loans	Dec. 31, 2013 Mezzanine loans	Jun. 30, 2014 Joint Venture Mezzanine loans	Jun. 30, 2014 Joint Venture Mezzanine loans
Investments in unconsolidated ventures
Number of significant unconsolidated joint ventures (investments)								1			1
Amount funded at initial closing of real estate private equity														$ 118,000,000						$ 282,100,000
Ownership interest held by the entity together with sponsor (as a percent)														51.00%
Ownership interest in amount funded (as a percent)														29.50%						70.50%	15.00%		15.00%		70.00%		15.00%
Number of real estate private equity funds contributed (funds)														49											24
Cash distribution to the Class B Partner (as a percent)															85.00%	51.00%
Cash distribution to the NorthStar Entities (as a percent)																	15.00%	85.00%	49.00%
Multiplier factor for cash distribution to the NorthStar Entities															1.5
Cash distribution after multiplier to entity and related party (percent)															15.00%
Investments in unconsolidated ventures								86,800,000			86,800,000		94,700,000								58,000,000		58,000,000	61,900,000
Equity in earnings (losses) of unconsolidated ventures	8,961,000	5,827,000	18,098,000	9,042,000				5,900,000		6,000,000	11,600,000	9,200,000									2,800,000		5,700,000								200,000	200,000
Net distribution received											19,600,000	23,700,000											10,600,000
Contribution made												7,500,000											1,100,000
Private equity investment estimated future capital commitments								6,000,000			6,000,000										2,000,000		2,000,000
Summarized financial information, net income (loss)									1,600,000
Summarized financial information, realized gains									1,900,000
Summarized financial information, realized losses									2,600,000
Aggregate reported net asset value																										910,000,000
Amount to be paid to the Seller for all of the fund interests																						504,800,000
Percentage of September 30, 2012 NAV paid as Initial Amount to Seller for all of the fund interests (percent)																						55.00%
Deferred amount of reported net asset value	400,000		400,000																		2,400,000	411,400,000	2,400,000
Percentage of September 30, 2012 NAV paid as Deferred Amount to Seller for all of the fund interests (percent)																						45.00%
Entity's share in Deferred Amount																							61,300,000
Period in which distribution will be made on priority basis since beginning, on the first day of the fiscal quarter following the closing date of each fund interest																							2 years
Reduction in deferred amount as a percentage of amortization amount (percent)																							15.00%
Investment percentage of distribution to seller (percent)																							15.00%
Investment percentage of distribution receivable after payment of deferred amount (percent)																							100.00%
Principal Amount	1,316,918,000		1,316,918,000		1,135,323,000																								181,193,000	186,693,000	183,700,000	183,700,000
Joint venture participating mortgage loan (percent)																															50.00%	50.00%
Real Estate Consolidated Joint Venture Ownership Interest																													78.00%
Real estate debt investments, net	1,259,805,000		1,259,805,000		1,074,773,000																								148,332,000	154,105,000	52,000,000	52,000,000
Ownership percentage (percent)																												35.00%
Ownership breakdown of total ownership (percent)						35.00%	65.00%
Realized gain on sale			$ 600,000