Debt Schedule of Long-Term Debt (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Debt Instrument [Line Items]
Long-term Debt	$ 215,284	$ 237,109
Long-term Debt, net of deferred financing costs	214,735	236,429
Loan Agreement
Debt Instrument [Line Items]
Long-term Debt	115,284	137,109
Less unamortized deferred financing fees
Debt Instrument [Line Items]
Less unamortized deferred financing fees	549	680
Four Point Six Seven Percent Senior Unsecured Notes Due Twenty Twenty One [Member] | Less unamortized deferred financing fees
Debt Instrument [Line Items]
Long-term Debt	$ 40,000	40,000
Interest rate	4.67%
Five Point Two Five Percent Senior Unsecured Notes Due Twenty Twenty Four [Member] | Less unamortized deferred financing fees
Debt Instrument [Line Items]
Long-term Debt	$ 11,000	11,000
Interest rate	5.25%
Five Point Three Zero Percent Senior Unsecured Notes Due Twenty Twenty Four [Member] | Less unamortized deferred financing fees
Debt Instrument [Line Items]
Long-term Debt	$ 29,000	29,000
Interest rate	5.30%
Five Point Four Five Percent Senior Unsecured Notes Due Twenty Twenty Six [Member] | Less unamortized deferred financing fees
Debt Instrument [Line Items]
Long-term Debt	$ 20,000	$ 20,000
Interest rate	5.45%