Fair Value Measurements - Carrying Value and Fair Value Measurements (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Level 2 | Carrying Value | Unsecured senior notes
Liabilities:
Debt instrument, fair value	$ 4,384,879	$ 4,390,189
Level 2 | Fair Value | Unsecured senior notes
Liabilities:
Debt instrument, fair value	4,585,089	4,682,432
Level 3 | Carrying Value
Liabilities:
Debt instrument, fair value	1,424,195	1,462,487
Level 3 | Fair Value
Liabilities:
Debt instrument, fair value	$ 1,427,979	$ 1,487,892