Debt Convertible Debt (Details) (USD $) Share data in Millions, except Per Share data, unless otherwise specified	12 Months Ended			1 Months Ended	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Nov. 30, 2010 Convertible Debt [Member]	Dec. 31, 2011 Convertible Debt [Member]	Dec. 31, 2010 Convertible Debt [Member]
Debt Instrument
Debt Instrument, Face Amount				$ 115,000,000	$ 115,000,000	$ 115,000,000
Debt Instrument, Interest Rate, Stated Percentage				3.25%	3.25%
Proceeds from Convertible Debt	0	115,000,000	0	111,000,000
Use of Debt Proceeds to Repay Borrowings on Revoloving Credit Agreement				62,200,000
Use of Debt Proceeds to Contribute to Qualified Pension Plan				25,000,000
Use of Debt Proceeds for the Purchase of Call Options Related to Convertible Note Offering				13,200,000
Convertible Debt, Features, Closing Sale Price of Common Stock Exceeding Current Converstion Price					130.00%
Conversion Feature, Percentage of Average of Closing Sale Price of Common Stock					98.00%
Purchase of call options related to convertible notes	0	13,225,000	0		13,200,000
Conversation Price Trading Days Prerequisite					20 days
Consecutive Trading Days Ending On The Last Trading Day Of The Previous Fiscal Quarter					30 days
Allows for acquistion of shares related to covertible debt					3.4
Proceeds from Issuance of Warrants	0	1,886,000	0		1,900,000
Conversion rate					29.4923	29.4499
Conversion price					$ 33.91	$ 33.96
Contingent conversion price					$ 44.08	$ 44.15
Warrant price					$ 44.34	$ 44.40
Convertible debt, carrying value of liability				101,700,000	103,522,000	101,843,000
Debt Instrument, Convertible, Carrying Amount of Equity Component				13,300,000	13,329,000	13,329,000
Present Value Discount Rate				5.25%
Amortization of Financing Costs				500,000
Deferred Finance Costs, Gross				3,100,000	3,600,000
Debt Instrument, Unamortized Discount					11,478,000	13,157,000
Contractual Coupon Rate of Interest Associated Interest Expense					3,737,000	401,000
Amortization of Debt Discount (Premium)	1,679,000	172,000	0		1,679,000	172,000
Debt Instrument, Convertible, Interest Expense					$ 5,416,000	$ 573,000
Debt Instrument, Convertible, Effective Interest Rate					5.25%