Borrowing Arrangements (Details) (USD $) In Thousands, unless otherwise specified					9 Months Ended					9 Months Ended			9 Months Ended
	Sep. 30, 2012	Dec. 31, 2011	Sep. 30, 2012 Revolving senior credit facility Bank of America as Administrative Agent, Issuing Lender and Lender	Dec. 31, 2011 Revolving senior credit facility Bank of America as Administrative Agent, Issuing Lender and Lender	Sep. 30, 2012 Revolving senior credit facility Bank of America as Administrative Agent, Issuing Lender and Lender Existing and future domestic guarantor subsidiaries	Sep. 30, 2012 Revolving senior credit facility Bank of America as Administrative Agent, Issuing Lender and Lender Existing and future foreign subsidiaries	Sep. 30, 2012 Revolving senior credit facility Bank of America as Administrative Agent, Issuing Lender and Lender LIBOR	Sep. 30, 2012 Revolving senior credit facility Bank of America as Administrative Agent, Issuing Lender and Lender LIBOR Low end of the range	Sep. 30, 2012 Revolving senior credit facility Bank of America as Administrative Agent, Issuing Lender and Lender LIBOR High end of the range	Sep. 30, 2012 Revolving senior credit facility Bank of America as Administrative Agent, Issuing Lender and Lender Base Rate	Sep. 30, 2012 Revolving senior credit facility Bank of America as Administrative Agent, Issuing Lender and Lender Base Rate Low end of the range	Sep. 30, 2012 Revolving senior credit facility Bank of America as Administrative Agent, Issuing Lender and Lender Base Rate High end of the range	Sep. 30, 2012 Revolving senior credit facility Bank of America as Administrative Agent, Issuing Lender and Lender Overnight federal funds rate	Sep. 30, 2012 Revolving senior credit facility Bank of America as Administrative Agent, Issuing Lender and Lender Bank of America, N.A. prime rate	Sep. 30, 2012 Letter of credit sub-facility Bank of America as Administrative Agent, Issuing Lender and Lender	Sep. 30, 2012 Swing line sub-facility Bank of America as Administrative Agent, Issuing Lender and Lender	Sep. 30, 2012 Capital lease obligations	Dec. 31, 2011 Capital lease obligations	Sep. 30, 2012 Obligations on seller notes and other	Dec. 31, 2011 Obligations on seller notes and other
Borrowing arrangements
Long-term borrowings	$ 73,291	$ 82,013	$ 71,800	$ 80,000													$ 558	$ 972	$ 933	$ 1,041
Less current portion	633	754
Long-term borrowings excluding current portion	72,658	81,259
Maximum borrowing capacity			210,000												50,000	10,000
Variable interest rate basis							One or two or three or six months LIBOR			Base Rate			federal funds rate	prime rate
Variable interest rate margin (as a percent)								2.00%	3.50%		0.50%	2.00%	0.50%
Percentage of stock of subsidiaries pledged to secure debt					100.00%	65.00%
Weighted average interest rate on senior credit facility (as a percent)			3.20%	3.10%
Weighted average interest rate on outstanding borrowings, not including letters of credit (as a percent)			3.20%	3.20%
Letters of credit outstanding															17,823
Available borrowing capacity			$ 38,674