Debt and Credit Arrangements Convertible Notes (Details) - USD ($) $ / shares in Units, shares in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Debt Instrument [Line Items]
Unamortized Debt Issuance Expense					$ 1,836,000
Interest accretion of convertible notes discount			$ 6,118,000	$ 5,654,000
Financing costs amortization	$ 321,000	$ 321,000	642,000	647,000
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	$ 221,752,000		221,752,000		215,634,000
Unamortized Debt Issuance Expense	1,481,000		1,481,000		1,836,000
Unamortized discount	28,248,000		28,248,000		$ 34,366,000
Debt Instrument, Convertible, Interest Expense	4,339,000	4,105,000	8,618,000	8,154,000
Interest Expense, Debt, Excluding Amortization	1,250,000	1,250,000	2,500,000	2,500,000
Interest accretion of convertible notes discount	3,089,000	2,855,000	6,118,000	5,654,000
Deferred Finance Costs, Gross	7,277,000		7,277,000
Financing costs amortization	$ 178,000	$ 178,000	$ 355,000	$ 356,000
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, Fair Value Disclosure, Narrative			The fair value of the Convertible Notes was approximately 94% and 88% of their par value as of June 30, 2016 and December 31, 2015, respectively.
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