Unconsolidated Subsidiaries (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013 Subsidiaries	Jun. 30, 2012	Dec. 31, 2012
Equity Method Investments and Joint Ventures [Abstract]
Number of wholly owned subsidiaries			2
Number of wholly owned unconsolidated subsidiaries			10
Investment in unconsolidated operations and related tax position	$ 34,500,000	$ 18,300,000	$ 34,500,000	$ 18,300,000	$ 20,200,000
Variable interest entity, reporting entity involvement, maximum risk of loss	4,200,000	4,900,000	4,200,000	4,900,000	3,200,000
Variable Interest Entity [Line Items]
Revenues	196,017,000	171,435,000	392,069,000	345,114,000
Gross profit	47,630,000	43,297,000	93,891,000	88,816,000
Net income	5,147,000	21,712,000	9,569,000	46,962,000
Variable Interest Entity, Not Primary Beneficiary
Variable Interest Entity [Line Items]
Revenues	141,302,000	135,004,000	280,938,000	269,382,000
Gross profit	17,515,000	18,236,000	37,012,000	37,399,000
Income before income taxes	10,695,000	11,018,000	23,478,000	23,597,000
Net income	$ 8,191,000	$ 8,915,000	$ 17,992,000	$ 18,397,000