Financing Arrangement - Financing Arrangement Activity (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Schedule of Joint Ventures [Line Items]
Interest income (expense)	$ (13,243)	$ (2,762)	$ (23,690)	$ 7,407
Joint Venture | Financing Arrangement
Schedule of Joint Ventures [Line Items]
Distributions of the partner's share of net income	1,982	2,464	3,879	4,466
Distributions in excess of the partner's share of net income	2,033	1,411	3,953	3,049
Adjustment to fair value of financing arrangement obligation	(17,258)	(8,768)	(31,522)	(4,386)
Interest income (expense)	$ (13,243)	$ (4,893)	$ (23,690)	$ 3,129