Financing Arrangement - Financing Arrangement Activity (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Schedule of Joint Ventures [Line Items]
Interest income (expense)	$ (10,447)	$ 10,169
Joint Venture | Financing Arrangement
Schedule of Joint Ventures [Line Items]
Distributions of the partner's share of net income	1,897	2,002
Distributions in excess of the partner's share of net income	1,921	1,638
Adjustment to fair value of financing arrangement obligation	(14,265)	4,382
Interest income (expense)	$ (10,447)	$ 8,022