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Debt Obligations, net - Schedule of Debt (Details)	1 Months Ended		3 Months Ended		9 Months Ended
Debt Obligations, net - Schedule of Debt (Details)	Sep. 30, 2019 USD ($)	Jun. 30, 2018 USD ($)	Sep. 30, 2020 USD ($) $ / shares	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($) $ / shares	Sep. 30, 2019 USD ($)	Aug. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Nov. 30, 2019 USD ($)	Oct. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)
Debt Instrument [Line Items]
Total debt obligations			$ 3,349,211,000		$ 3,349,211,000			$ 3,436,038,000
Debt discounts and deferred financing costs, net			(41,528,000)		(41,528,000)			(48,958,000)
Total debt obligations, net			3,307,683,000		3,307,683,000			3,387,080,000
Interest costs capitalized			$ 500,000	$ 500,000	$ 1,600,000	$ 6,900,000
Senior Term Loan \| LIBOR
Debt Instrument [Line Items]
Basis point spread on variable interest rate (as a percent)					1.00%
3.125% Senior Convertible Notes
Debt Instrument [Line Items]
Stated interest rates (as a percent)	3.125%		3.125%	3.125%	3.125%	3.125%
Secured Credit Facility and Mortgages
Debt Instrument [Line Items]
Total debt obligations			$ 1,236,711,000		$ 1,236,711,000			1,212,993,000
Debt discounts and deferred financing costs, net			(6,447,000)		(6,447,000)
Total debt obligations, net			1,230,264,000		1,230,264,000
Secured Credit Facility and Mortgages \| Revolving Credit Facility
Debt Instrument [Line Items]
Total debt obligations			20,000,000		$ 20,000,000			0
Debt instrument term (in years)					1 year
Secured Credit Facility and Mortgages \| Revolving Credit Facility \| Federal Funds Rate
Debt Instrument [Line Items]
Basis point spread on variable interest rate (as a percent)					0.50%
Secured Credit Facility and Mortgages \| Revolving Credit Facility \| LIBOR
Debt Instrument [Line Items]
Basis point spread on variable interest rate (as a percent)					2.00%
Secured Credit Facility and Mortgages \| Revolving Credit Facility \| LIBOR \| Minimum
Debt Instrument [Line Items]
Basis point spread on variable interest rate (as a percent)	2.00%				1.00%
Secured Credit Facility and Mortgages \| Revolving Credit Facility \| LIBOR \| Minimum \| Interest Rate Category Two
Debt Instrument [Line Items]
Basis point spread on variable interest rate (as a percent)					2.00%
Secured Credit Facility and Mortgages \| Revolving Credit Facility \| LIBOR \| Maximum
Debt Instrument [Line Items]
Basis point spread on variable interest rate (as a percent)	2.50%
Secured Credit Facility and Mortgages \| Revolving Credit Facility \| LIBOR \| Maximum \| Interest Rate Category Two
Debt Instrument [Line Items]
Basis point spread on variable interest rate (as a percent)					2.50%
Secured Credit Facility and Mortgages \| Revolving Credit Facility \| Base Rate \| Minimum
Debt Instrument [Line Items]
Basis point spread on variable interest rate (as a percent)	1.00%
Secured Credit Facility and Mortgages \| Revolving Credit Facility \| Base Rate \| Minimum \| Interest Rate Category One
Debt Instrument [Line Items]
Basis point spread on variable interest rate (as a percent)					1.00%
Secured Credit Facility and Mortgages \| Revolving Credit Facility \| Base Rate \| Maximum
Debt Instrument [Line Items]
Basis point spread on variable interest rate (as a percent)	1.50%
Secured Credit Facility and Mortgages \| Revolving Credit Facility \| Base Rate \| Maximum \| Interest Rate Category One
Debt Instrument [Line Items]
Basis point spread on variable interest rate (as a percent)					1.50%
Secured Credit Facility and Mortgages \| Senior Term Loan
Debt Instrument [Line Items]
Total debt obligations			491,875,000		$ 491,875,000			491,875,000
Debt instrument, face amount		$ 650,000,000.0
Secured Credit Facility and Mortgages \| Senior Term Loan \| Federal Funds Rate
Debt Instrument [Line Items]
Basis point spread on variable interest rate (as a percent)					0.50%
Secured Credit Facility and Mortgages \| Senior Term Loan \| LIBOR
Debt Instrument [Line Items]
Basis point spread on variable interest rate (as a percent)		2.75%			2.75%
Secured Credit Facility and Mortgages \| Senior Term Loan \| LIBOR \| Maximum
Debt Instrument [Line Items]
Basis point spread on variable interest rate (as a percent)					1.75%
Secured Credit Facility and Mortgages \| Mortgages Collateralized by Net Lease Assets
Debt Instrument [Line Items]
Total debt obligations			$ 724,836,000		$ 724,836,000			721,118,000
Weighted average interest rate (as a percent)			4.40%		4.40%
Secured Credit Facility and Mortgages \| Mortgages Collateralized by Net Lease Assets \| Minimum
Debt Instrument [Line Items]
Stated interest rates (as a percent)			1.70%		1.70%
Secured Credit Facility and Mortgages \| Mortgages Collateralized by Net Lease Assets \| Maximum
Debt Instrument [Line Items]
Stated interest rates (as a percent)			7.26%		7.26%
Unsecured Notes
Debt Instrument [Line Items]
Total debt obligations			$ 2,012,500,000		$ 2,012,500,000			2,123,045,000
Unsecured Notes \| 6.00% Senior Notes
Debt Instrument [Line Items]
Total debt obligations			$ 0		$ 0			$ 110,545,000
Stated interest rates (as a percent)			6.00%		6.00%			6.00%
Unsecured Notes \| 5.25% Senior Notes
Debt Instrument [Line Items]
Total debt obligations			$ 0		$ 0			$ 400,000,000
Stated interest rates (as a percent)			5.25%		5.25%
Unsecured Notes \| 3.125% Senior Convertible Notes
Debt Instrument [Line Items]
Total debt obligations			$ 287,500,000		$ 287,500,000			287,500,000
Total debt obligations, net			$ 273,500,000		$ 273,500,000			$ 268,700,000
Stated interest rates (as a percent)	3.125%		3.125%	3.125%	3.125%	3.125%		3.125%		3.125%
Convertible debt, conversion ratio (in shares per par value)					0.0697134
Convertible debt, conversion price (in dollars per share) \| $ / shares			$ 14.34		$ 14.34
Liability component of convertible debt										$ 34,000,000.0	$ 221,800,000
Equity component of convertible debt										3,400,000	$ 22,500,000
Debt instrument, face amount										$ 37,500,000
Unamortized discount			$ 11,600,000		$ 11,600,000			$ 15,500,000
Contractual interest			2,200,000	$ 2,200,000	6,700,000	$ 6,700,000
Amortization of debt discount			$ 1,300,000	$ 1,300,000	$ 3,900,000	$ 3,700,000
Effective interest rate (as a percent)			5.20%		5.20%
Unsecured Notes \| 4.75% Senior Notes
Debt Instrument [Line Items]
Total debt obligations			$ 775,000,000		$ 775,000,000			775,000,000
Stated interest rates (as a percent)	4.75%		4.75%	4.75%	4.75%	4.75%			4.75%
Debt instrument, face amount	$ 675,000,000.0			$ 675,000,000.0		$ 675,000,000.0			$ 100,000,000.0
Effective interest rate (as a percent)									4.29%
Unsecured Notes \| 4.25% Senior Notes
Debt Instrument [Line Items]
Total debt obligations			$ 550,000,000		$ 550,000,000			$ 550,000,000
Stated interest rates (as a percent)			4.25%		4.25%			4.25%
Debt instrument, face amount								$ 550,000,000.0
Unsecured Notes \| 5.50% Senior Notes
Debt Instrument [Line Items]
Total debt obligations			$ 400,000,000		$ 400,000,000			0
Stated interest rates (as a percent)			5.50%		5.50%		5.50%
Debt instrument, face amount							$ 400,000,000.0
Other Debt Obligations \| Trust Preferred Securities
Debt Instrument [Line Items]
Total debt obligations			$ 100,000,000		$ 100,000,000			$ 100,000,000
Other Debt Obligations \| Trust Preferred Securities \| LIBOR
Debt Instrument [Line Items]
Basis point spread on variable interest rate (as a percent)					1.50%