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Debt Obligations, net (Schedule of Debt) (Details) | 1 Months Ended | 12 Months Ended |  |  |  |
--- | --- | --- | --- | --- | --- | ---
Sep. 30, 2019 USD ($) | Jun. 30, 2019 USD ($) | Jun. 30, 2018 USD ($) | Dec. 31, 2020 USD ($) $ / shares | Dec. 31, 2019 USD ($) | Dec. 31, 2018 USD ($) | Aug. 31, 2020 USD ($) | Nov. 30, 2019 USD ($) | Oct. 31, 2017 USD ($) | Sep. 30, 2017 USD ($)
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Total debt obligations |  |  |  |  | $ 3,325,450,000 | $ 3,436,038,000 |  |  |  |  |
Debt discounts and deferred financing costs, net |  |  |  |  | (38,475,000) | (48,958,000) |  |  |  |  |
Total debt obligations, net | [1] |  |  |  | 3,286,975,000 | 3,387,080,000 |  |  |  |  |
Interest costs capitalized |  |  |  |  | $ 1,900,000 | 7,500,000 | $ 11,300,000 |  |  |  |
Net Lease Asset |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Non-recourse debt assumed by buyer |  |  | $ 228,000,000.0 |  |  | 228,000,000.0 |  |  |  |  |
Senior Term Loan | LIBOR |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Basis point spread on variable interest rate |  |  |  |  | 1.00% |  |  |  |  |  |
3.125% senior convertible notes |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Stated interest rate |  |  |  |  | 3.125% |  |  |  |  |  |
Secured credit facilities and mortgages |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Total debt obligations |  |  |  |  | $ 1,212,950,000 | 1,212,993,000 |  |  |  |  |
Debt discounts and deferred financing costs, net |  |  |  |  | (6,010,000) |  |  |  |  |  |
Total debt obligations, net |  |  |  |  | 1,206,940,000 |  |  |  |  |  |
Assets served as collateral |  |  |  |  | 2,100,000,000 |  |  |  |  |  |
Secured credit facilities and mortgages | Revolving Credit Facility |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Total debt obligations |  |  |  |  | $ 0 | 0 |  |  |  |  |
Secured credit facilities and mortgages | Revolving Credit Facility | Federal Funds Rate |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Basis point spread on variable interest rate |  |  |  |  | 0.50% |  |  |  |  |  |
Secured credit facilities and mortgages | Revolving Credit Facility | LIBOR |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Basis point spread on variable interest rate |  |  |  |  | 2.00% |  |  |  |  |  |
Debt instrument term |  |  |  |  | 1 year |  |  |  |  |  |
Secured credit facilities and mortgages | Revolving Credit Facility | LIBOR | Minimum |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Basis point spread on variable interest rate |  | 2.00% |  |  | 1.00% |  |  |  |  |  |
Secured credit facilities and mortgages | Revolving Credit Facility | LIBOR | Minimum | Interest Rate Category Two |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Basis point spread on variable interest rate |  |  |  |  | 2.00% |  |  |  |  |  |
Secured credit facilities and mortgages | Revolving Credit Facility | LIBOR | Maximum |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Basis point spread on variable interest rate |  | 2.50% |  |  |  |  |  |  |  |  |
Secured credit facilities and mortgages | Revolving Credit Facility | LIBOR | Maximum | Interest Rate Category Two |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Basis point spread on variable interest rate |  |  |  |  | 2.50% |  |  |  |  |  |
Secured credit facilities and mortgages | Revolving Credit Facility | Base Rate | Minimum |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Basis point spread on variable interest rate |  | 1.00% |  |  |  |  |  |  |  |  |
Secured credit facilities and mortgages | Revolving Credit Facility | Base Rate | Minimum | Interest Rate Category One |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Basis point spread on variable interest rate |  |  |  |  | 1.00% |  |  |  |  |  |
Secured credit facilities and mortgages | Revolving Credit Facility | Base Rate | Maximum |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Basis point spread on variable interest rate |  | 1.50% |  |  |  |  |  |  |  |  |
Secured credit facilities and mortgages | Revolving Credit Facility | Base Rate | Maximum | Interest Rate Category One |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Basis point spread on variable interest rate |  |  |  |  | 1.50% |  |  |  |  |  |
Secured credit facilities and mortgages | Senior Term Loan |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Total debt obligations |  |  |  |  | $ 491,875,000 | 491,875,000 |  |  |  |  |
Debt instrument, face amount |  |  |  | $ 650,000,000.0 |  |  |  |  |  |  |
Secured credit facilities and mortgages | Senior Term Loan | Federal Funds Rate |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Basis point spread on variable interest rate |  |  |  |  | 0.50% |  |  |  |  |  |
Secured credit facilities and mortgages | Senior Term Loan | LIBOR |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Basis point spread on variable interest rate |  |  |  | 2.75% | 2.75% |  |  |  |  |  |
Secured credit facilities and mortgages | Senior Term Loan | LIBOR | Maximum |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Basis point spread on variable interest rate |  |  |  |  | 1.75% |  |  |  |  |  |
Secured credit facilities and mortgages | Mortgages collateralized by net lease assets |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Total debt obligations |  |  |  |  | $ 721,075,000 | 721,118,000 |  |  |  |  |
Weighted average interest rate |  |  |  |  | 4.40% |  |  |  |  |  |
Secured credit facilities and mortgages | Mortgages collateralized by net lease assets | Minimum |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Stated interest rate |  |  |  |  | 1.69% |  |  |  |  |  |
Secured credit facilities and mortgages | Mortgages collateralized by net lease assets | Maximum |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Stated interest rate |  |  |  |  | 7.26% |  |  |  |  |  |
Unsecured notes |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Total debt obligations |  |  |  |  | $ 2,012,500,000 | 2,123,045,000 |  |  |  |  |
Unsecured notes | 6.00% senior notes |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Total debt obligations |  |  |  |  | $ 0 | $ 110,545,000 |  |  |  |  |
Stated interest rate |  |  |  |  | 6.00% | 6.00% |  |  |  |  |
Unsecured notes | 5.25% senior notes |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Total debt obligations |  |  |  |  | $ 0 | $ 400,000,000 |  |  |  |  |
Stated interest rate |  |  |  |  | 5.25% |  |  | 5.25% |  |  |
Debt instrument, face amount |  |  |  |  |  |  |  | $ 400,000,000.0 |  |  |
Unsecured notes | 3.125% senior convertible notes |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Total debt obligations |  |  |  |  | $ 287,500,000 | 287,500,000 |  |  |  |  |
Total debt obligations, net |  |  |  |  | $ 275,100,000 | $ 268,700,000 |  |  |  |  |
Stated interest rate |  |  |  |  | 3.125% | 3.125% |  |  |  | 3.125% |
Convertible debt conversion ratio (in shares per par value) |  |  |  |  | 0.07025 |  |  |  |  |  |
Convertible debt conversion price (in dollars per share) | $ / shares |  |  |  |  | $ 14.23 |  |  |  |  |  |
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 |  |  |  |  | $ 10,200,000 | $ 15,500,000 |  |  |  |  |
Contractual interest |  |  |  |  | 9,000,000.0 | 9,000,000.0 | 9,000,000.0 |  |  |  |
Amortization of debt discount |  |  |  |  | $ 5,200,000 | $ 5,000,000.0 | $ 4,700,000 |  |  |  |
Effective interest rate |  |  |  |  | 5.20% | 5.20% | 5.20% |  |  |  |
Unsecured notes | 4.75% senior notes |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Total debt obligations |  |  |  |  | $ 775,000,000 | $ 775,000,000 |  |  |  |  |
Stated interest rate |  | 4.75% |  |  | 4.75% |  |  |  | 4.75% |  |
Debt instrument, face amount |  | $ 675,000,000.0 |  |  |  |  |  |  | $ 100,000,000.0 |  |
Effective interest rate |  |  |  |  |  |  |  |  | 4.29% |  |
Unsecured notes | 4.25% senior notes |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Total debt obligations |  |  |  |  | $ 550,000,000 | $ 550,000,000 |  |  |  |  |
Stated interest rate |  |  |  |  | 4.25% | 4.25% |  |  |  |  |
Debt instrument, face amount |  |  |  |  |  | $ 550,000,000.0 |  |  |  |  |
Unsecured notes | 5.5% senior notes |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Total debt obligations |  |  |  |  | $ 400,000,000 | 0 |  |  |  |  |
Stated interest rate |  |  |  |  | 5.50% |  |  |  |  |  |
Other debt obligations | Trust preferred securities |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Total debt obligations |  |  |  |  | $ 100,000,000 | $ 100,000,000 |  |  |  |  |
Other debt obligations | Trust preferred securities | LIBOR |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Basis point spread on variable interest rate |  |  |  |  | 1.50% |  |  |  |  |  |
[1] | Refer to Note 2 for details on the Company's consolidated variable interest entities ("VIEs").

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