Long-Term Debt and Credit Agreements - Schedule of long term debt (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Debt Instrument [Line Items]
Long-term Debt	$ 237,109	$ 45,200
Less: Unamortized debt issuance expense	680	853
Long-term debt, excluding unamortized deferred financing costs	236,429	44,347
Credit Agreement [Member]
Debt Instrument [Line Items]
Long-term Debt	137,109	34,200
Senior Notes [Member]
Debt Instrument [Line Items]
Long-term Debt	100,000
4.67% Senior Unsecured Notes due 2021 [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Long-term Debt	40,000
5.25% Unsecured Notes due in 2024 [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Long-term Debt	11,000	11,000
5.30% Senior Unsecured Notes due 2024 | Senior Notes [Member]
Debt Instrument [Line Items]
Long-term Debt	29,000
5.45% Senior Unsecured Notes due 2026 | Senior Notes [Member]
Debt Instrument [Line Items]
Long-term Debt	$ 20,000	$ 0