Fair Value Measurements Net Profits Plan (Details) - USD ($)		3 Months Ended	12 Months Ended
		Mar. 31, 2016	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Period of New York Mercantile Exchange Strip Pricing Used for Price Forecast		5 years
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Net Profits Plan Liability Noncurrent		$ 7,611,000
Net Profits Plan Liability Noncurrent		$ 6,351,000	$ 7,611,000
Net Profit Plan liability [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Inputs, Discount Rate		10.00%	10.00%
Period of New York Mercantile Exchange Strip Pricing Used for Price Forecast		5 years
Period Used for Price Assumptions of Strip Prices for Liabilities		1 year
Percent Change in Commodity Prices for Sensitivity Analysis		5.00%
Sensitivity Analysis Change in Liability, Due to Change in Commodity Prices		$ 1,000,000
Percent Increase and Decrease in Discount Rate for Sensitivity Analysis		1.00%
Sensitivity Analysis Change in Liability Due to Change in Discount Rate		$ (250,000)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Net Profits Plan Liability Noncurrent		7,611,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Period Increase (Decrease)	[1]	(291,000)
Net settlements (1) (2)	[1],[2]	(969,000)
Transfers in (out) of Level 3		0
Net Profits Plan Liability Noncurrent		$ 6,351,000	$ 7,611,000

[1] Net changes in the Company’s Net Profits Plan liability are shown in the Change in Net Profits Plan liability line item of the accompanying statements of operations.

[2] Settlements represent cash payments made or accrued under the Net Profits Plan.