Long-Term Debt (Detail Textuals 1) (USD $) In Millions, unless otherwise specified	12 Months Ended				12 Months Ended
	Dec. 31, 2012	Dec. 31, 2008 Interest Rate Swap	Dec. 31, 2008 Credit facility	Dec. 31, 2012 Credit facility	Dec. 31, 2012 Credit facility Minimum	Dec. 31, 2012 Credit facility Maximum	Dec. 31, 2012 Credit facility Option 1 A	Dec. 31, 2012 Credit facility Option 1 A Minimum	Dec. 31, 2012 Credit facility Option 1 A Maximum	Dec. 31, 2012 Credit facility Option 1 B	Dec. 31, 2012 Credit facility Option 1 C	Dec. 31, 2012 Credit facility Option 2 Eurodollar Borrowings	Dec. 31, 2012 Credit facility Option 2 Eurodollar Borrowings Minimum	Dec. 31, 2012 Credit facility Option 2 Eurodollar Borrowings Maximum
Line of Credit Facility [Line Items]
Percentage of commitment fee for the unused portion of the credit facility					0.25%	0.35%
Threshold limit of ratio of debt to earnings before interest taxes depreciation and amortization	no more than 2.5 to 1
Threshold limit of ratio of earnings before interest taxes depreciation and amortization to interest expenses	no less than 2 to 1
Line of credit facility, amount outstanding for self insurance programs and contract bids				$ 18.1
Amount of interest rate swap agreement		$ 50.0	$ 18.1
Debt instrument, interest rate, basis for effective rate			2.07%
Basis spread on variable rate										0.50%	1.00%
Line of Credit Facility, Interest Rate Description							prime rate			Federal Funds Rate	LIBOR rate	Adjusted LIBOR
Line Of Credit Facility Margin Percentage								0.25%	1.25%				1.25%	2.25%