Long-Term Debt and Credit Facility - Debt Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Long-term debt, term note and notes payable:
Other notes with interest rates from 3.3% to 6.5%	$ 9,797	$ 12,600
Total	355,422	377,475
Less – Current maturities and notes payable	17,648	26,399
Long-term debt, less current maturities	$ 337,774	$ 351,076
2015 Credit Facility
Debt Instrument [Line Items]
Current annualized interest rate	2.61%	2.61%
Long-term debt, term note and notes payable:
Term notes	$ 345,625	$ 0
2013 Credit Facility
Debt Instrument [Line Items]
Current annualized interest rate	2.17%	2.17%
Long-term debt, term note and notes payable:
Term notes	$ 0	$ 319,375
Line of credit, 2.16% in 2014	$ 0	$ 45,500
2011 Credit Facility
Debt Instrument [Line Items]
Current annualized interest rate	2.16%	2.16%
Long-term debt, term note and notes payable:
Line of credit, 2.16% in 2014	$ 0	$ 45,500
Minimum
Debt Instrument [Line Items]
Current annualized interest rate	3.30%	3.30%
Maximum
Debt Instrument [Line Items]
Current annualized interest rate	6.50%	6.50%