Debt (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014		Dec. 31, 2013
Short-term debt:
Bank Credit Facility, expires July 30, 2019	$ 38,000		$ 38,000
Long-term debt, current and noncurrent:
Long-term debt	199,923		199,874
Total	237,923	[1]	237,874	[1]
Senior Notes 2015 [Member] | Senior Note 6.05 % [Member]
Long-term debt, current and noncurrent:
Long-term debt	74,982	[1]	74,962	[1]
Senior Notes 2016 [Member] | Senior Note 6.85 % [Member]
Long-term debt, current and noncurrent:
Long-term debt	$ 124,941	[1]	$ 124,912	[1]

[1] The Company designates debt obligations as “long-term” based on maturity date at issuance.