Derivative Instruments (Narrative) (Details) - USD ($)	Dec. 31, 2015	Dec. 31, 2014
Derivative Instruments And Hedging Activities Disclosure [Abstract]
Net derivative assets	$ 18,400	$ 18,700
Current portion of put premiums payable-affiliate	8,500	6,500
Long-term put premiums payable-affiliate	$ 0	$ 7,500