Property, Plant and Equipment - Schedule of Property, Plant and Equipment (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 578,924	$ 425,189
Less accumulated depreciation, depletion and amortization	162,123	143,318
Property, plant and equipment, net	416,801	281,871
Machinery, equipment and automotive [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	319,088	253,317
Machinery, equipment and automotive [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Useful lives in years	3 years
Machinery, equipment and automotive [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Useful lives in years	30 years
Buildings and improvements [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	48,379	44,248
Buildings and improvements [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Useful lives in years	8 years
Buildings and improvements [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Useful lives in years	30 years
Furniture, fixtures and store equipment [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	6,933	6,718
Furniture, fixtures and store equipment [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Useful lives in years	3 years
Furniture, fixtures and store equipment [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Useful lives in years	10 years
Assets under capital leases [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	1,672	1,468
Useful lives in years	10 years
Land improvements [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	6,214	1,148
Land improvements [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Useful lives in years	10 years
Land improvements [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Useful lives in years	40 years
Proved natural gas properties [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	66,764	49,801
Construction in progress [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	110,376	52,673
Capital spare parts [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	9,718	5,430
Land [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 9,780	$ 10,386