Fair Value Measurements of Financial Instruments (Details) (Recurring, Commodity Derivatives, USD $) In Thousands, unless otherwise specified	Mar. 31, 2015 item	Dec. 31, 2014 item
Significant Other Observable Inputs (Level 2)
Fair Value Measurements of Financial Instruments
Number of bank counterparties for company's commodity derivative contracts	7	7
Assets:
Total assets	$ 95,473	$ 126,709
Significant Other Observable Inputs (Level 2) | Swaps | NGL
Assets:
Total assets	79,344	106,450
Significant Other Observable Inputs (Level 2) | Swaps | Gas
Assets:
Total assets	16,129	20,259
Total
Assets:
Total assets	95,473	126,709
Total | Swaps | NGL
Assets:
Total assets	79,344	106,450
Total | Swaps | Gas
Assets:
Total assets	$ 16,129	$ 20,259