Long-Term Debt and Credit Arrangements (Details) $ in Thousands			12 Months Ended
	Dec. 12, 2015 USD ($)	Oct. 28, 2015 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Sep. 30, 2015 USD ($)
Debt Instrument [Line Items]
Total debt			$ 260,105	$ 276,868
Less: current maturities			15,024	1,247
Total long-term debt			245,081	275,621
Long-term Debt, Fiscal Year Maturity [Abstract]
Long-term Debt, Maturities, Repayments of Principal in 2016			15,000
Long-term Debt, Maturities, Repayments of Principal in 2017			45,000
Long-term Debt, Maturities, Repayments of Principal in 2018			46,300
Long-term Debt, Maturities, Repayments of Principal in 2019			50,000
Long-term Debt, Maturities, Repayments of Principal in 2020			103,800
Long-term debt			245,081	270,105
Current maturities of long-term debt			15,024	21
Proceeds from long-term debt			30,000	0	$ 0
Letters of Credit Outstanding, Amount			$ 19,100
Covenant Compliance			We were in compliance with the covenants contained in our senior note agreements and Credit Agreement.
Consolidated Interest Coverage Ratio, Actual			10.05
Consolidated Interest Coverage Ratio, Covenant			4.00
Institutional Groups One and Two (As Amended March 2014) [Member]
Long-term Debt, Fiscal Year Maturity [Abstract]
Consolidated Leverage Ratio, Maximum, After Quarter Ending September 30, 2014			3.00
Senior notes payable [Member]
Debt Instrument [Line Items]
Total debt			$ 100,000	70,000
Senior notes payable [Member] | Institutional Group Two [Member]
Debt Instrument [Line Items]
Total debt			$ 160,000
Long-term Debt, Fiscal Year Maturity [Abstract]
Debt Instrument, Interest Rate, Stated Percentage			6.11%
Senior notes payable [Member] | Institutional Group Two [Member] | London Interbank Offered Rate (LIBOR) [Member]
Long-term Debt, Fiscal Year Maturity [Abstract]
Derivative, Variable Interest Rate			4.15%
Senior Notes [Member]
Debt Instrument [Line Items]
Total debt			$ 160,000	200,000
Senior Notes [Member] | 2019 Notes [Member]
Long-term Debt, Fiscal Year Maturity [Abstract]
Debt, Current			40,000
Long-term debt			30,000
Mortgages payable [Member]
Debt Instrument [Line Items]
Total debt			0	6,742
Other notes payables [Member]
Debt Instrument [Line Items]
Total debt			105	$ 126
Line of Credit [Member]
Long-term Debt, Fiscal Year Maturity [Abstract]
Line of Credit Facility, Maximum Borrowing Capacity		$ 300,000	200,000			$ 215,000
Proceeds from long-term debt	$ 30,000	$ 70,000
Line of Credit Facility, Remaining Borrowing Capacity			$ 181,000
Debt Instrument, Basis Spread on Variable Rate, LIBOR Loans			1.75%
Debt Instrument, Basis Spread on Variable Rate			0.75%
Consolidated Fixed Charge Coverage Ratio, Minimum, Collateral Release Period			1.25
Consolidated Leverage Ratio, Maximum, Collateral Release Period			2.50
Line of Credit [Member] | Minimum [Member]
Long-term Debt, Fiscal Year Maturity [Abstract]
Line of Credit Facility, Interest Rate at Period End			2.36%
Line of Credit [Member] | Maximum [Member]
Long-term Debt, Fiscal Year Maturity [Abstract]
Line of Credit Facility, Interest Rate at Period End			4.25%
Line of Credit [Member] | Institutional Groups One and Two (As Amended March 2014) [Member]
Long-term Debt, Fiscal Year Maturity [Abstract]
Consolidated Tangible Net Worth, Actual			$ 822,800
Consolidated Tangible Net Worth, Covenant			$ 659,600
Adjusted Consolidated Leverage Ratio, Actual			1.83
Letter of Credit [Member]
Long-term Debt, Fiscal Year Maturity [Abstract]
Line of Credit Facility, Maximum Borrowing Capacity			$ 100,000
Term Loan [Member]
Long-term Debt, Fiscal Year Maturity [Abstract]
Long-term debt			95,000
Line of Credit Facility, Maximum Borrowing Capacity			$ 100,000
Long-term Debt, Percentage Of Loan To Be Paid In Eleven Installments, Beginning March 2016			1.25%
Long-term Debt, Percentage Of Loan To Be Paid In Eight Installments, Beginning In December 2018			2.50%
Current maturities of long-term debt			$ 5,000