Long-Term Debt - Narrative (Details) (USD $)	6 Months Ended
	Jun. 30, 2013	Dec. 31, 2012
Long-Term Debt (Textual) [Abstract]
Current portion of long-term debt	$ 27,200,000	$ 15,900,000
Long-term debt (less current portion)	160,950,000	180,200,000
Scheduled principal payments on long-term debt in 2013	8,000,000
Scheduled principal payments on long-term debt in 2014	26,500,000
Scheduled principal payments on long-term debt in 2015	26,500,000
Scheduled principal payments on long-term debt in 2016	127,200,000
Percentage of commitment fees of total unused commitment under revolving credit facility	0.50%
Letters of credit outstanding amount	200,000	1,100,000
Financing Agreement
Long-Term Debt (Textual) [Abstract]
Revolving credit and term loan agreement to finance acquisition	312,000,000
Restricted payment for dividend and share repurchase, maximum	25,000,000
Additional restricted payment for dividend and share repurchase, maximum	250,000,000
Restriction amount related to acquisitions maximum	25,000,000
Restriction amount related to acquisitions based on financial results and condition maximum	150,000,000
Financing Agreement | Minimum
Long-Term Debt (Textual) [Abstract]
LIBOR plus margin range	3.50%
Financing Agreement | Maximum
Long-Term Debt (Textual) [Abstract]
LIBOR plus margin range	4.00%
Financing Agreement | Term loan
Long-Term Debt (Textual) [Abstract]
Revolving credit and term loan agreement to finance acquisition	212,000,000
Base interest rate	3.70%	3.72%
Current portion of long-term debt	6,000,000
Weighted average interest rate	3.70%	4.25%
Financing Agreement | Revolving Credit Facility
Long-Term Debt (Textual) [Abstract]
Revolving credit and term loan agreement to finance acquisition	$ 100,000,000