Unconsolidated Subsidiaries (Details) (USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2013 Subsidiaries	Mar. 31, 2012	Dec. 31, 2012 Subsidiaries
Unconsolidated Subsidiaries [Abstract]
Number of wholly owned subidiaries			2
Number of wholly owned unconsolidated subsidiaries	10
Variable interest entity, ownership percentage by parent			100.00%
Investment in unconsolidated operations and related tax position	$ 37,200,000		$ 20,200,000
Variable interest entity, reporting entity involvement, maximum risk of loss	5,100,000		3,200,000
Variable Interest Entity [Line Items]
Revenues	196,052,000	173,679,000
Gross profit	46,261,000	45,519,000
Net income	4,422,000	25,250,000
Variable Interest Entity, Not Primary Beneficiary
Variable Interest Entity [Line Items]
Revenues	139,636,000	134,378,000
Gross profit	19,497,000	19,163,000
Income before income taxes	12,783,000	12,579,000
Net income	$ 9,801,000	$ 9,482,000