Debt (Convertible Debt) (Details) $ / shares in Units, $ in Thousands		1 Months Ended	12 Months Ended
		Nov. 30, 2010 USD ($) shares	Dec. 31, 2016 USD ($) $ / shares shares		Dec. 31, 2015 USD ($) $ / shares shares		Dec. 31, 2014 USD ($)	Nov. 20, 2012 $ / shares
Interest Expense, Debt [Abstract]
Contractual coupon rate of interest			$ 3,738		$ 3,738		$ 3,738
Accretion of convertible notes discount			2,144		2,035		1,931
Interest expense			5,882		5,773		5,669
Revolving Credit Facility
Debt Instrument
Use of debt proceeds to repay borrowings on revolving credit agreement		$ 62,200
Convertible Notes
Debt Instrument
Convertible notes face amount		$ 115,000	$ 115,000		$ 115,000
Annual principal interest rate		3.25%
Proceeds from convertible debt		$ 111,000
Use of debt proceeds to contribute to qualified pension plan		25,000
Use of debt proceeds for the purchase of call options related to convertible note offering		$ 13,200
Convertible Debt [Abstract]
Conversion rate		29.4499	29.9134	[1]	29.8059	[1]
Conversion price | $ / shares			$ 33.4298	[2]	$ 33.5504	[2]		$ 33.96
Contingent conversion price | $ / shares	[3]		$ 43.46		$ 43.62
Aggregate shares to be issued upon conversion, convertible | shares	[4]		3,440,045		3,427,679
Percentage of conversion price			130.00%
Conversation price trading days prerequisite			20 days
Consecutive trading days ending on the last trading day of the previous fiscal quarter			30 days
Convertible debt, number of consecutive days priors to threshold trading days			5 days
Convertible, threshold consecutive trading days			5 days
Percentage of average of closing price of common stock			98.00%
Conversion percentage of principal amount			100.00%
Purchase of call options related to convertible notes		$ 13,200
Allows for acquisition of shares related to convertible debt | shares		3,400,000
Proceeds from issuance of warrants		$ 1,900
Warrant price | $ / shares			$ 43.72		$ 43.87
Present value discount rate		5.25%
Deferred finance costs, gross		$ 3,600	$ 3,100
Amortization of financing costs		500	600		$ 500		$ 500
Unamortized discount			1,797		3,942
Carrying value of liability		101,700	113,203		111,058
Equity component		$ 13,300	13,329		$ 13,329
Convertible debt, if-converted value in excess of principal			$ 45,000

[1] Represents the number of shares of Common Stock hypothetically issuable per $1,000 principal amount of Notes, subject to adjustments per the Convertible Note Indenture dated November 19, 2010. At the date the Company issued the Convertible Notes, the conversion rate initially equaled 29.4499 shares of common stock per $1,000 principal amount of notes (which is equivalent to an initial conversion price of approximately $33.96 per share of common stock). The conversion rate is subject to adjustment upon the occurrence of certain specified events, such as an increase in the dividend paid to shareholders.

[2] Represents $1,000 divided by the conversion rate as of such date. The conversion price reflects the strike price of the embedded option within the Convertible Note. Were the Company's share price to exceed the conversion price at conversion the noteholders would be entitled to receive additional consideration either in cash, shares or a combination thereof, the form of which is at the sole discretion of the Company.

[3] Prior to May 15, 2017, the notes are convertible only in the following circumstances: (1) during any fiscal quarter commencing after April 1, 2011, and only during any such fiscal quarter, if the last reported sale price of our common stock was greater than or equal to 130% of the applicable conversion price for at least 20 trading days (whether or not consecutive) during the 30 consecutive trading days ending on the last trading day of the previous fiscal quarter, (2) upon the occurrence of specified corporate transactions, or (3) during the five consecutive business-day period following any five consecutive trading-day period in which, for each day of that period, the trading price for the notes was less than 98% of the product of the last reported sale price of our common stock and the applicable conversion rate on such trading day. On and after May 15, 2017, until the close of business on the second scheduled trading day immediately preceding the maturity date, holders may convert their notes at any time, regardless of the foregoing circumstances. Upon a change in control or termination of trading, holders of the notes may require us to repurchase all or a portion of their notes for cash at a repurchase price equal to 100% of the principal amount, plus any accrued and unpaid interest.

[4] This represents the number of shares hypothetically issuable upon conversion of the principal balance of the Convertible Notes at each date; however, as the terms of the Convertible Notes require net share settlement, the aggregate principal amount of the notes will be paid in cash. Amounts due in excess of the principal, if any, may be settled in cash, shares of the Company's common stock or a combination of cash and shares of common stock, at the Company's election.