Segment Information - Operating results (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Revenues
Revenues	$ 51,924	$ 28,761	$ 97,083	$ 55,112
Operating income (loss)
Operating income (loss)	4,023	728	3,969	702
Corporate and other business activities	(11,715)	(7,977)	(22,618)	(15,689)
Interest income, net	488	1,246	1,209	1,869
Other income (expense), net	654	(1,278)	3,582	(139)
Income from continuing operations before income taxes and equity method income	5,165	696	8,760	2,432
Depreciation and amortization	6,014	4,831	12,177	9,825
Energy segment:
Revenues
Revenues	47,153	27,071	91,066	53,110
Operating income (loss)
Operating income (loss)	7,905	3,392	13,372	6,619
Depreciation and amortization	5,612	4,682	11,405	9,537
Sports segment:
Revenues
Revenues	4,771	1,690	6,017	2,002
Operating income (loss)
Operating income (loss)	(10)	(307)	(2,042)	(1,293)
Depreciation and amortization	402	149	772	288
Total segment operating income
Operating income (loss)
Operating income (loss)	7,895	3,085	11,330	5,326
Corporate and other business activities
Operating income (loss)
Corporate and other business activities	$ (3,872)	$ (2,357)	$ (7,361)	$ (4,624)