Amount of income (loss) for proportionate share of equity method investee's income (loss).

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Investment in Laramie Energy, LLC - Change in Equity Investment (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Beginning balance			$ 136,656
Equity losses from Laramie Energy	$ 491	$ (2,352)	792	$ 3,224
Ending balance	137,448		137,448
Laramie Energy Company
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Beginning balance			136,656
Equity losses from Laramie Energy			(2,553)
Accretion of basis difference			3,345
Ending balance	$ 137,448		$ 137,448