Fair Value Measurements - Carrying Values and Fair Values of Financial Instruments (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Liabilities carried at historical cost on the consolidated balance sheets
Deferred financing costs, net	$ 9,242	$ 0
Reported Value Measurement | Fair Value, Inputs, Level 2
Assets carried at historical cost on the consolidated balance sheets
Investments in debt securities	209,386	209,337
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 2
Assets carried at historical cost on the consolidated balance sheets
Investments in debt securities	209,744	209,390
Secured Debt
Liabilities carried at historical cost on the consolidated balance sheets
Deferred financing costs, net	5,053	9,256
Secured Debt | Reported Value Measurement | Fair Value, Inputs, Level 2
Liabilities carried at historical cost on the consolidated balance sheets
Liabilities carried at historical cost	4,233,578	5,263,994
Secured Debt | Estimate of Fair Value Measurement | Fair Value, Inputs, Level 2
Liabilities carried at historical cost on the consolidated balance sheets
Liabilities carried at historical cost	4,245,640	5,265,180
Unsecured Debt
Liabilities carried at historical cost on the consolidated balance sheets
Deferred financing costs, net	14,134
Unsecured Debt | Reported Value Measurement | Fair Value, Inputs, Level 3
Liabilities carried at historical cost on the consolidated balance sheets
Liabilities carried at historical cost	1,500,000	0
Unsecured Debt | Estimate of Fair Value Measurement | Fair Value, Inputs, Level 3
Liabilities carried at historical cost on the consolidated balance sheets
Liabilities carried at historical cost	1,501,639	0
Loans Payable
Liabilities carried at historical cost on the consolidated balance sheets
Deferred financing costs, net		6,044
Loans Payable | Reported Value Measurement | Fair Value, Inputs, Level 3
Liabilities carried at historical cost on the consolidated balance sheets
Liabilities carried at historical cost	0	2,321,585
Loans Payable | Estimate of Fair Value Measurement | Fair Value, Inputs, Level 3
Liabilities carried at historical cost on the consolidated balance sheets
Liabilities carried at historical cost	$ 0	$ 2,329,551