Debt - Schedule of Debt (Details) kr in Billions	6 Months Ended
	Jun. 30, 2020 USD ($) extension property debt_instrument	Jun. 30, 2020 NOK (kr) property	Dec. 31, 2019 USD ($)
Debt Instrument [Line Items]
Principal amount	$ 2,919,670,000		$ 3,199,923,000
Carrying value	2,908,407,000		3,188,498,000
Mortgage and other notes payable, net	1,174,146,000		1,256,112,000
Investment grade notes | CLNC 2019-FL1
Debt Instrument [Line Items]
Principal amount	840,423,000		840,423,000
Carrying value	$ 834,088,000		833,153,000
Net lease 6 | Collateralized by a property in Company's Core Portfolio
Debt Instrument [Line Items]
Contractual interest rate	4.45%	4.45%
Net lease 5 | Collateralized by a property in Company's Core Portfolio
Debt Instrument [Line Items]
Contractual interest rate	4.08%	4.08%
Net lease 5 | Collateralized by a property in Legacy, Non-Strategic Portfolio
Debt Instrument [Line Items]
Contractual interest rate	4.45%	4.45%
Net lease 4 | Collateralized by a property in Legacy, Non-Strategic Portfolio
Debt Instrument [Line Items]
Contractual interest rate	4.45%	4.45%
Net lease 3 | Collateralized by a property in Company's Core Portfolio
Debt Instrument [Line Items]
Contractual interest rate	4.77%	4.77%
Net lease 3 | Collateralized by a property in Legacy, Non-Strategic Portfolio
Debt Instrument [Line Items]
Contractual interest rate	4.00%	4.00%
Net lease 1 | Collateralized by a property in Company's Core Portfolio
Debt Instrument [Line Items]
Contractual interest rate	4.31%	4.31%
Net lease 1 | Collateralized by a property in Legacy, Non-Strategic Portfolio
Debt Instrument [Line Items]
Contractual interest rate	4.45%	4.45%
Net lease 1 | Collateralized by properties in Legacy, Non-Strategic Portfolio
Debt Instrument [Line Items]
Contractual interest rate	4.38%	4.38%
Net lease 2
Debt Instrument [Line Items]
Mortgage and other notes payable, net	$ 165,300,000	kr 1.6
Net lease 2 | Collateralized by a property in Company's Core Portfolio
Debt Instrument [Line Items]
Contractual interest rate	3.91%	3.91%
Other real estate 4 | Collateralized by a property in Legacy, Non-Strategic Portfolio
Debt Instrument [Line Items]
Contractual interest rate	4.84%	4.84%
Other real estate 2 | Collateralized by a property in Legacy, Non-Strategic Portfolio
Debt Instrument [Line Items]
Contractual interest rate	4.94%	4.94%
Other real estate 8 | Collateralized by a property in Legacy, Non-Strategic Portfolio
Debt Instrument [Line Items]
Contractual interest rate	3.53%	3.53%
Other real estate 10
Debt Instrument [Line Items]
Number of instruments | debt_instrument	2
Weighted average interest rate (in percentage)	3.53%	3.53%
Other real estate 10 | Collateralized by a property in Legacy, Non-Strategic Portfolio
Debt Instrument [Line Items]
Contractual interest rate	3.53%	3.53%
Other real estate 9 | Collateralized by a property in Legacy, Non-Strategic Portfolio
Debt Instrument [Line Items]
Contractual interest rate	3.98%	3.98%
Other real estate 1 | Collateralized by a property in Legacy, Non-Strategic Portfolio
Debt Instrument [Line Items]
Contractual interest rate	4.47%	4.47%
Other real estate 3 | Collateralized by a property in Legacy, Non-Strategic Portfolio
Debt Instrument [Line Items]
Contractual interest rate	4.30%	4.30%
Securitization bonds payable, net
Debt Instrument [Line Items]
Principal amount	$ 840,423,000		840,423,000
Carrying value	$ 834,088,000		833,153,000
Securitization bonds payable, net | Minimum
Debt Instrument [Line Items]
Initial debt term (in years)	2 years
Securitization bonds payable, net | Maximum
Debt Instrument [Line Items]
Initial debt term (in years)	3 years
Securitization bonds payable, net | CLNC 2019-FL1 | LIBOR
Debt Instrument [Line Items]
Interest rate margin (in percentage)	1.59%
Mortgage and other notes payable, net
Debt Instrument [Line Items]
Principal amount	$ 1,179,074,000		1,260,267,000
Carrying value	1,174,146,000		1,256,112,000
Mortgage and other notes payable, net | Net lease 6 | Collateralized by a property in Company's Core Portfolio
Debt Instrument [Line Items]
Principal amount	23,906,000		24,117,000
Carrying value	23,906,000		24,117,000
Mortgage and other notes payable, net | Net lease 6 | Collateralized by a property in Legacy, Non-Strategic Portfolio
Debt Instrument [Line Items]
Principal amount	1,514,000		1,658,000
Carrying value	$ 1,477,000		1,615,000
Mortgage and other notes payable, net | Net lease 6 | Collateralized by a property in Legacy, Non-Strategic Portfolio | LIBOR
Debt Instrument [Line Items]
Interest rate margin (in percentage)	2.15%
Mortgage and other notes payable, net | Net lease 5 | Collateralized by a property in Company's Core Portfolio
Debt Instrument [Line Items]
Principal amount	$ 31,582,000		31,821,000
Carrying value	31,321,000		31,539,000
Mortgage and other notes payable, net | Net lease 5 | Collateralized by a property in Legacy, Non-Strategic Portfolio
Debt Instrument [Line Items]
Principal amount	3,389,000		3,422,000
Carrying value	3,303,000		3,329,000
Mortgage and other notes payable, net | Net lease 4 | Collateralized by a property in Company's Core Portfolio
Debt Instrument [Line Items]
Principal amount	75,871,000		74,916,000
Carrying value	75,677,000		74,845,000
Mortgage and other notes payable, net | Net lease 4 | Collateralized by a property in Legacy, Non-Strategic Portfolio
Debt Instrument [Line Items]
Principal amount	7,306,000		7,384,000
Carrying value	$ 7,121,000		7,184,000
Mortgage and other notes payable, net | Net lease 4 | Collateralized by a property in Legacy, Non-Strategic Portfolio | LIBOR
Debt Instrument [Line Items]
Interest rate margin (in percentage)	2.50%
Mortgage and other notes payable, net | Net lease 3 | Collateralized by a property in Company's Core Portfolio
Debt Instrument [Line Items]
Principal amount	$ 200,000,000		200,000,000
Carrying value	198,562,000		198,521,000
Mortgage and other notes payable, net | Net lease 3 | Collateralized by a property in Legacy, Non-Strategic Portfolio
Debt Instrument [Line Items]
Principal amount	12,364,000		12,450,000
Carrying value	12,310,000		12,368,000
Mortgage and other notes payable, net | Net lease 1 | Collateralized by a property in Company's Core Portfolio
Debt Instrument [Line Items]
Principal amount	250,000,000		250,000,000
Carrying value	247,224,000		246,961,000
Mortgage and other notes payable, net | Net lease 1 | Collateralized by a property in Legacy, Non-Strategic Portfolio
Debt Instrument [Line Items]
Principal amount	18,402,000		18,579,000
Carrying value	17,935,000		18,076,000
Mortgage and other notes payable, net | Net lease 1 | Collateralized by properties in Legacy, Non-Strategic Portfolio
Debt Instrument [Line Items]
Principal amount	12,166,000		12,221,000
Carrying value	$ 11,729,000		11,758,000
Number of properties | property	3	3
Mortgage and other notes payable, net | Net lease 2 | Collateralized by a property in Company's Core Portfolio
Debt Instrument [Line Items]
Principal amount	$ 165,312,000		181,952,000
Carrying value	167,656,000		184,532,000
Mortgage and other notes payable, net | Other real estate 4 | Collateralized by a property in Legacy, Non-Strategic Portfolio
Debt Instrument [Line Items]
Principal amount	42,545,000		42,925,000
Carrying value	$ 42,966,000		43,407,000
Debt term extension available (in years)	1 year
Mortgage and other notes payable, net | Other real estate 2 | Collateralized by a property in Legacy, Non-Strategic Portfolio
Debt Instrument [Line Items]
Principal amount	$ 0		42,443,000
Carrying value	0		42,851,000
Mortgage and other notes payable, net | Other real estate 8 | Collateralized by a property in Legacy, Non-Strategic Portfolio
Debt Instrument [Line Items]
Principal amount	22,880,000		15,819,000
Carrying value	22,587,000		16,324,000
Mortgage and other notes payable, net | Other real estate 10 | Collateralized by a property in Legacy, Non-Strategic Portfolio
Debt Instrument [Line Items]
Principal amount	12,482,000		11,744,000
Carrying value	12,296,000		11,939,000
Mortgage and other notes payable, net | Other real estate 9 | Collateralized by a property in Legacy, Non-Strategic Portfolio
Debt Instrument [Line Items]
Principal amount	23,657,000		23,885,000
Carrying value	22,904,000		23,133,000
Mortgage and other notes payable, net | Other real estate 1 | Collateralized by a property in Legacy, Non-Strategic Portfolio
Debt Instrument [Line Items]
Principal amount	107,871,000		108,719,000
Carrying value	108,532,000		109,475,000
Mortgage and other notes payable, net | Other real estate 3 | Collateralized by a property in Legacy, Non-Strategic Portfolio
Debt Instrument [Line Items]
Principal amount	74,579,000		75,256,000
Carrying value	73,946,000		74,554,000
Mortgage and other notes payable, net | Other real estate 5 | Collateralized by a property in Legacy, Non-Strategic Portfolio
Debt Instrument [Line Items]
Principal amount	0		33,498,000
Carrying value	$ 0		32,801,000
Mortgage and other notes payable, net | Other real estate 5 | Collateralized by a property in Legacy, Non-Strategic Portfolio | LIBOR
Debt Instrument [Line Items]
Interest rate margin (in percentage)	4.00%
Mortgage and other notes payable, net | Other real estate 6 | Collateralized by a property in Legacy, Non-Strategic Portfolio
Debt Instrument [Line Items]
Principal amount	$ 21,500,000		21,500,000
Carrying value	$ 20,946,000		20,825,000
Number of optional extensions to initial maturity date | extension	2
Mortgage and other notes payable, net | Other real estate 6 | Collateralized by a property in Legacy, Non-Strategic Portfolio | LIBOR
Debt Instrument [Line Items]
Interest rate margin (in percentage)	2.95%
Mortgage and other notes payable, net | Loan 9
Debt Instrument [Line Items]
Principal amount	$ 71,748,000		65,958,000
Carrying value	$ 71,748,000		65,958,000
Mortgage and other notes payable, net | Loan 9 | LIBOR
Debt Instrument [Line Items]
Interest rate margin (in percentage)	3.00%
Mortgage and other notes payable, net | Net lease 1, periodic payment of principal and interest
Debt Instrument [Line Items]
Number of properties | property	2	2
Mortgage and other notes payable, net | Net lease 1, periodic payment of interest
Debt Instrument [Line Items]
Number of properties | property	1	1
Mortgage and other notes payable, net | Other notes payable
Debt Instrument [Line Items]
Number of optional extensions to initial maturity date | extension	3
Debt term extension available (in years)	1 year
Bank credit facility
Debt Instrument [Line Items]
Principal amount	$ 195,000,000		113,500,000
Carrying value	$ 195,000,000		113,500,000
Bank credit facility | Bank credit facility
Debt Instrument [Line Items]
Number of optional extensions to initial maturity date | extension	2
Debt term extension available (in years)	6 months
Credit facilities
Debt Instrument [Line Items]
Principal amount	$ 900,173,000		1,099,233,000
Carrying value	900,173,000		1,099,233,000
Credit facilities | Master repurchase facilities
Debt Instrument [Line Items]
Capacity	2,250,000,000
Principal amount	666,821,000		780,211,000
Carrying value	$ 666,821,000		780,211,000
Percent of recourse of the financed amount	25.00%	25.00%
Credit facilities | CMBS credit facilities
Debt Instrument [Line Items]
Contractual interest rate	4.25%	4.25%
Principal amount	$ 38,352,000		205,522,000
Carrying value	$ 38,352,000		205,522,000
Credit facilities | CMBS credit facilities | Minimum
Debt Instrument [Line Items]
Initial debt term (in years)	1 month
Credit facilities | CMBS credit facilities | Maximum
Debt Instrument [Line Items]
Initial debt term (in years)	3 months
Credit facilities | LIBOR
Debt Instrument [Line Items]
Interest rate margin (in percentage)	2.25%
Credit facilities | LIBOR | Master repurchase facilities | Minimum
Debt Instrument [Line Items]
Interest rate margin (in percentage)	1.50%
Credit facilities | LIBOR | Master repurchase facilities | Maximum
Debt Instrument [Line Items]
Interest rate margin (in percentage)	2.60%
Credit facilities | Bank credit facility
Debt Instrument [Line Items]
Capacity	$ 450,000,000
Principal amount	195,000,000		113,500,000
Carrying value	195,000,000		113,500,000
Credit facilities | Bank 1 facility 3 | Master repurchase facilities
Debt Instrument [Line Items]
Capacity	400,000,000
Principal amount	104,559,000		106,309,000
Carrying value	$ 104,559,000		106,309,000
Number of optional extensions to initial maturity date | extension	2
Debt term extension available (in years)	1 year
Credit facilities | Bank 1 facility 3 | LIBOR | Master repurchase facilities
Debt Instrument [Line Items]
Interest rate margin (in percentage)	1.91%
Credit facilities | Bank 2 facility 3 | Master repurchase facilities
Debt Instrument [Line Items]
Capacity	$ 200,000,000
Principal amount	21,353,000		22,750,000
Carrying value	$ 21,353,000		22,750,000
Number of optional extensions to initial maturity date | extension	2
Debt term extension available (in years)	1 year
Credit facilities | Bank 2 facility 3 | LIBOR | Master repurchase facilities
Debt Instrument [Line Items]
Interest rate margin (in percentage)	2.50%
Credit facilities | Bank 3 facility 3 | Master repurchase facilities
Debt Instrument [Line Items]
Capacity	$ 600,000,000
Principal amount	207,176,000		265,633,000
Carrying value	$ 207,176,000		265,633,000
Credit facilities | Bank 3 facility 3 | LIBOR | Master repurchase facilities
Debt Instrument [Line Items]
Interest rate margin (in percentage)	2.15%
Credit facilities | Bank 7 facility 1 | Master repurchase facilities
Debt Instrument [Line Items]
Capacity	$ 500,000,000
Principal amount	181,396,000		221,421,000
Carrying value	$ 181,396,000		221,421,000
Debt term extension available (in years)	1 year
Credit facilities | Bank 7 facility 1 | LIBOR | Master repurchase facilities
Debt Instrument [Line Items]
Interest rate margin (in percentage)	1.93%
Credit facilities | Bank 8 facility 1 | Master repurchase facilities
Debt Instrument [Line Items]
Capacity	$ 250,000,000
Principal amount	152,337,000		164,098,000
Carrying value	$ 152,337,000		164,098,000
Debt term extension available (in years)	1 year
Credit facilities | Bank 8 facility 1 | LIBOR | Master repurchase facilities
Debt Instrument [Line Items]
Interest rate margin (in percentage)	2.00%
Credit facilities | Bank 9 Facility 1 | Master repurchase facilities
Debt Instrument [Line Items]
Capacity	$ 300,000,000
Principal amount	0		0
Carrying value	$ 0		0
Number of optional extensions to initial maturity date | extension	2
Debt term extension available (in years)	1 year
Credit facilities | Bank 9 Facility 1 | Master repurchase facilities | Minimum
Debt Instrument [Line Items]
Percent of recourse of the financed amount	25.00%	25.00%
Credit facilities | Bank 9 Facility 1 | Master repurchase facilities | Maximum
Debt Instrument [Line Items]
Percent of recourse of the financed amount	50.00%	50.00%
Credit facilities | Bank 1 facility 1 | CMBS credit facilities
Debt Instrument [Line Items]
Principal amount	$ 0		20,375,000
Carrying value	0		20,375,000
Credit facilities | Bank 1 facility 2 | CMBS credit facilities
Debt Instrument [Line Items]
Principal amount	0		18,834,000
Carrying value	0		18,834,000
Credit facilities | Bank 3 facility | CMBS credit facilities
Debt Instrument [Line Items]
Principal amount	0		0
Carrying value	0		0
Credit facilities | Bank 4 facility | CMBS credit facilities
Debt Instrument [Line Items]
Principal amount	0		0
Carrying value	0		0
Credit facilities | Bank 5 facility 1 | CMBS credit facilities
Debt Instrument [Line Items]
Principal amount	0		0
Carrying value	0		0
Credit facilities | Bank 5 facility 2 | CMBS credit facilities
Debt Instrument [Line Items]
Principal amount	0		0
Carrying value	$ 0		0
Credit facilities | Bank 6 facility 1 | CMBS credit facilities
Debt Instrument [Line Items]
Contractual interest rate	4.25%	4.25%
Principal amount	$ 23,122,000		83,584,000
Carrying value	$ 23,122,000		83,584,000
Credit facilities | Bank 6 facility 2 | CMBS credit facilities
Debt Instrument [Line Items]
Contractual interest rate	4.25%	4.25%
Principal amount	$ 15,230,000		82,729,000
Carrying value	$ 15,230,000		$ 82,729,000