Debt and Credit Arrangements Convertible Notes (Details) (USD $) Share data in Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013
Debt Instrument [Line Items]
Class of Warrant or Right, Exercise Price of Warrants or Rights	84.96		84.96
Current convertible notes	$ 0		$ 0		$ 193,437,000
Interest accretion of convertible notes discount			7,917,000	7,317,000
Financing costs amortization	326,000	326,000	979,000	979,000
Convertible Notes, Due 2018 [Member] | Convertible Debt [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	250,000,000		250,000,000
Debt Instrument, Interest Rate, Stated Percentage	2.00%		2.00%
Debt Instrument, Convertible, Effective Interest Rate	7.90%		7.90%
Number Of Shares Of Convertible Debt Hedged And Capped Call	3,622		3,622
Class of Warrant or Right, Exercise Price of Warrants or Rights	84.96		84.96
Proceeds from Issuance of Warrants			48,848,000
Net Cost Of Convertible Note Hedge And All Capped Transactions			17,638,000
Convertible Debt, Noncurrent	201,354,000		201,354,000
Current convertible notes					193,437,000
Unamortized discount	48,646,000		48,646,000		56,563,000
Debt Instrument, Convertible, Interest Expense	3,941,000	3,737,000	11,667,000	11,067,000
Interest Expense, Debt, Excluding Amortization	1,250,000	1,250,000	3,750,000	3,750,000
Interest accretion of convertible notes discount	2,691,000	2,487,000	7,917,000	7,317,000
Deferred Finance Costs, Gross	7,277,000		7,277,000
Financing costs amortization	178,000	178,000	533,000	533,000
Debt Instrument, Convertible, Threshold Consecutive Trading Days			20 days
Debt Instrument, Convertible, Threshold Trading Days			30
Debt Instrument, Convertible, Threshold Percentage of Stock Price Trigger			130.00%
Debt Instrument, Convertible, Conversion Price	$ 69.03		$ 69.03
Maximum Days After Any Five Trading Day Period In Which Trading Price Was Less Than 97 Percent Of Last Reported Sale Price of Common Stock Times Conversion Rate			5 days
Convertible Notes Principal Amount Denominator For Trading Price	1,000		1,000
Maximum Allowable Percentage Of The Product Of Last Reported Sale Price of Common Stock And Conversion Rate For Convertible Notes Payable	97.00%		97.00%
Percent Of The Principal Amount Of The Convertible Notes Plus Accrued Interest To Be Purchased By The Company Subject Company Undergoing A Fundamental Change	100.00%		100.00%
Debt Instrument, Convertible, Carrying Amount of Equity Component	48,646,000		48,646,000
Debt Instrument, Fair Value Disclosure, Narrative			The fair value of the Convertible Notes was approximately 117% of their par value as of September 30, 2014 and approximately 154% of their par value as of December 31, 2013. The Convertible Notes are actively quoted instruments and, accordingly, the fair value of the Convertible Notes was determined using Level 1 inputs as defined in Note 8.
Liability Component [Member] | Convertible Notes, Due 2018 [Member] | Convertible Debt [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	170,885,000		170,885,000
Deferred Finance Costs, Gross	4,974,000		4,974,000
Equity Component [Member] | Convertible Notes, Due 2018 [Member] | Convertible Debt [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	79,115,000		79,115,000
Deferred Finance Costs, Gross	$ 2,303,000		$ 2,303,000