Unconsolidated Subsidiaries (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014 Subsidiaries	Jun. 30, 2013	Dec. 31, 2013
Variable Interest Entity [Line Items]
Number of wholly owned subsidiaries			2
Number of wholly owned unconsolidated subsidiaries			10
Variable interest entity, reporting entity involvement, maximum risk of loss	$ 4,500,000	$ 4,200,000	$ 4,500,000	$ 4,200,000	$ 5,400,000
Accounts receivable from affiliates	36,351,000	29,029,000	36,351,000	29,029,000	32,636,000
Revenues	200,370,000	196,017,000	377,783,000	392,069,000
Gross profit	36,523,000	47,630,000	72,694,000	93,891,000
Net income (loss)	(3,624,000)	5,147,000	(5,148,000)	9,569,000
Coyote Creek
Variable Interest Entity [Line Items]
Accounts receivable from affiliates	32,500,000	25,900,000	32,500,000	25,900,000	27,900,000
Other Noncurrent Assets
Variable Interest Entity [Line Items]
Investment in unconsolidated operations and related tax position	30,300,000	34,500,000	30,300,000	34,500,000	33,100,000
Liberty
Variable Interest Entity [Line Items]
Current production capacity	500,000		500,000
Production capacity in 2019	4,700,000		4,700,000
Variable Interest Entity, Not Primary Beneficiary
Variable Interest Entity [Line Items]
Revenues	148,075,000	141,302,000	286,598,000	280,938,000
Gross profit	17,126,000	17,515,000	36,619,000	37,012,000
Income before income taxes	10,994,000	10,695,000	24,162,000	23,478,000
Net income (loss)	$ 8,530,000	$ 8,191,000	$ 18,674,000	$ 17,992,000