Debt and Preferred Equity Investments - Debt Investments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Mortgage loans on real estate, interest rate	8.42%
Debt Investments Held [Abstract]
Carrying value	$ 1,580,306	$ 2,099,393
Mezzanine Loan with an Initial Maturity Date of March 2020
Debt Investments Held [Abstract]
Amount participated out	1,300
Mezzanine Loan with an Initial Maturity Date of June 2024
Debt Investments Held [Abstract]
Amount participated out	12,000
Mortgage/Mezzanine Loan With An Initial Maturity Due April 2021
Debt Investments Held [Abstract]
Amount participated out	96,400
Debt investment
Debt Investments Held [Abstract]
Future Funding Obligations	138,672
Senior Financing	5,288,939
Carrying value	1,341,070	1,812,936
Total fixed rate
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	4,115,114
Carrying Value	646,612	430,099
Total fixed rate | Mezzanine Loan with an Initial Maturity Date of March 2020
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	1,160,000
Carrying Value	222,775	213,185
Total fixed rate | Mezzanine Loan with an Initial Maturity Date of September 2021
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	15,000
Carrying Value	3,500	3,500
Total fixed rate | Mezzanine Loan with an Initial Maturity Date of April 2022
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	147,000
Carrying Value	24,952	24,932
Total fixed rate | Mezzanine Loan With An Initial Maturity Of August 2022
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	280,000
Carrying Value	38,734	36,585
Total fixed rate | Mezzanine Loan With Maturity June 2023
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	326,574
Carrying Value	215,737	0
Total fixed rate | Mezzanine Loan, with an Initial Maturity Date of November 2023
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	83,790
Carrying Value	12,714	12,706
Total fixed rate | Mezzanine Loan With An Initial Maturity Date Of December 2023
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	180,000
Carrying Value	30,000	30,000
Total fixed rate | Mezzanine Loan with an Initial Maturity Date of June 2024
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	115,000
Carrying Value	12,950	12,941
Total fixed rate | Mezzanine Loan, with an Initial Maturity Date of January 2025
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	95,000
Carrying Value	30,000	30,000
Total fixed rate | Mezzanine Loan with an Initial Maturity Date of June 2027
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	1,712,750
Carrying Value	55,250	55,250
Total fixed rate | Mezzanine Loan Sold In 2019
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	0
Carrying Value	0	11,000
Total floating rate
Debt Investments Held [Abstract]
Future Funding Obligations	138,672
Senior Financing	1,173,825
Carrying value	694,458	1,382,837
Total floating rate | Mezzanine Loan with an Initial Maturity of January 2020
Debt Investments Held [Abstract]
Future Funding Obligations	2,509
Senior Financing	29,420
Carrying value	82,696	62,493
Total floating rate | Mortgage/Mezzanine Loan Due March 2020
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	0
Carrying value	69,839	0
Total floating rate | Mortgage and Mezzanine Loan with an Initial Maturity Date of April 2020
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	40,000
Carrying value	20,000	19,986
Total floating rate | Mezzanine Loan with an Initial Maturity of July 2020
Debt Investments Held [Abstract]
Future Funding Obligations	4,831
Senior Financing	47,302
Carrying value	15,743	12,627
Total floating rate | Mortgage/Mezzanine Loan Due August 2020
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	0
Carrying value	19,971	19,999
Total floating rate | Mezzanine Loan Due September 2020
Debt Investments Held [Abstract]
Future Funding Obligations	44,737
Senior Financing	0
Carrying value	106,473	88,501
Total floating rate | Mortgage And Mezzanine Loan With An Initial Maturity Date Of October 2020
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	63,990
Carrying value	55,573	83,449
Total floating rate | Mezzanine Loan Due December 2021
Debt Investments Held [Abstract]
Future Funding Obligations	19,212
Senior Financing	421,938
Carrying value	51,387	88,817
Total floating rate | Mortgage/Mezzanine Loan with an Initial Maturity of December 2020
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	0
Carrying value	35,386	35,266
Total floating rate | Mortgage/Mezzanine Loan With An Initial Maturity Due April 2021
Debt Investments Held [Abstract]
Future Funding Obligations	10,384
Senior Financing	0
Carrying value	96,570	277,694
Total floating rate | Mezzanine Loan With An Initial Maturity Due April 2021
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	275,000
Carrying value	49,809	24,961
Total floating rate | Jr Mortgage Participation/Mezzanine Loan with an Initial Maturity of July 2021
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	60,000
Carrying value	15,698	15,665
Total floating rate | Mezzanine Loan With An Initial Maturity Due July 2021
Debt Investments Held [Abstract]
Future Funding Obligations	12,999
Senior Financing	151,175
Carrying value	41,395	0
Total floating rate | Mezzanine Loan Due December 2022
Debt Investments Held [Abstract]
Future Funding Obligations	44,000
Senior Financing	0
Carrying value	13,918	0
Total floating rate | Mezzanine Loan Due December 2029
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	85,000
Carrying value	20,000	0
Total floating rate | Mezzanine Loan Repaid In 2019
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	0
Carrying value	0	53,402
Total floating rate | Mezzanine Loan Repaid In 2019, 2
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	0
Carrying value	0	79,164
Total floating rate | Mezzanine Loan Repaid In 2019, 3
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	0
Carrying value	0	15,333
Total floating rate | Mezzanine Loan Repaid In 2019, 4
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	0
Carrying value	0	14,822
Total floating rate | Mortgage And Mezzanine Loan Repaid In 2019
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	0
Carrying value	0	154,070
Total floating rate | Mezzanine Loan Repaid In 2019, 5
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	0
Carrying value	0	34,886
Total floating rate | Mortgage/Jr.Mortgage Participation Loan Repaid In 2019
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	0
Carrying value	0	84,012
Total floating rate | Mortgage And Mezzanine Loan Repaid In 2019, 2
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	0
Carrying value	0	37,094
Total floating rate | Mortgage And Mezzanine Loan Repaid In 2019, 3
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	0
Carrying value	0	98,804
Total floating rate | Mezzanine Loan Repaid In 2019, 6
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	0
Carrying value	0	7,305
Total floating rate | Mezzanine Loan Repaid In 2019, 7
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	0
Carrying value	0	14,998
Total floating rate | Mezzanine Loan Repaid In 2019, 8
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	0
Carrying value	0	21,990
Total floating rate | Mezzanine Loan Repaid In 2019, 9
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	0
Carrying value	$ 0	$ 37,499