Segment Information - Operating results (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Revenues
Revenues	$ 58,583	$ 31,420	$ 155,666	$ 86,532
Operating income (loss)
Operating income (loss)	6,180	949	10,149	1,651
Corporate and other business activities	(11,804)	(7,131)	(34,422)	(22,820)
Interest income, net	554	472	1,763	2,341
Other income (expense), net	(1,299)	1,467	2,283	1,408
Income from continuing operations before income taxes and equity method income	5,435	2,888	14,195	5,400
Depreciation and amortization	5,950	4,536	18,127	14,361
Energy segment:
Revenues
Revenues	49,701	25,162	140,767	78,272
Operating income (loss)
Operating income (loss)	8,551	2,007	21,923	8,626
Depreciation and amortization	5,519	4,386	16,924	13,923
Sports segment:
Revenues
Revenues	8,882	6,258	14,899	8,260
Operating income (loss)
Operating income (loss)	1,146	975	(896)	(318)
Depreciation and amortization	431	150	1,203	438
Total segment operating income
Operating income (loss)
Operating income (loss)	9,697	2,982	21,027	8,308
Corporate and other business activities
Operating income (loss)
Corporate and other business activities	$ (3,517)	$ (2,033)	$ (10,878)	$ (6,657)