Fair Value Measurements - Carrying Value and Fair Value Measurements (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Level 2 | Carrying Value | Unsecured senior notes
Liabilities:
Debt instrument, fair value	$ 4,323,063	$ 4,390,189
Level 2 | Fair Value | Unsecured senior notes
Liabilities:
Debt instrument, fair value	4,212,628	4,682,432
Level 3 | Carrying Value
Liabilities:
Debt instrument, fair value	1,433,372	1,462,487
Level 3 | Fair Value
Liabilities:
Debt instrument, fair value	$ 1,426,786	$ 1,487,892