Investment in Piceance Energy Summarized Financial Information (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014		Dec. 31, 2014
ASSETS
Current assets	$ 390,517			$ 460,789
Current liabilities	280,814			310,806
Natural gas and oil revenues	476	1,577
Income (loss) from operations	17,857	(14,802)
Net loss	462	(14,568)	[1]
Piceance Energy [Member]
ASSETS
Current assets	10,185			13,168
Non-current assets	471,837			468,379
Current liabilities	15,320			17,103
Non-current liabilities	77,944			107,087
Natural gas and oil revenues	10,737	20,243
Income (loss) from operations	(7,079)	3,609
Net loss	$ (6,080)	$ (1,091)

[1] Entities with a net loss are prohibited from including potential common shares in the computation of diluted per share amounts. We have utilized the basic shares outstanding to calculate both basic and diluted loss per share for the three months ended March 31, 2014.