Debt and Credit Arrangements Convertible Notes (Details) (USD $) Share data in Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Debt Instrument [Line Items]
Minimum Trading Days Required During Thirty Consecutive Trading Days Where Last Reported Sales Price Is At Least 130 Percent Of Conversion Price	20 days		20 days
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		5 days
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%
Current convertible notes	$ 188,413,000		$ 188,413,000		$ 0
Convertible notes conversion feature	61,587,000		61,587,000		0
Class of Warrant or Right, Exercise Price of Warrants or Rights	84.96		84.96
Interest accretion of convertible notes discount			4,830,000	4,465,000
Financing costs amortization	327,000	556,000	653,000	877,000
Share Price	$ 94.09		$ 94.09
Debt Instrument, Convertible, If-converted Value in Excess of Principal	90,758,000
Assets And Liabilities For Which Fair Value Only Is Disclosed, Fair Value Of Convertible Notes As A Percentage Of Par Value	152.00%		152.00%		124.00%
Convertible Notes Payable [Member] | Convertible Notes, Due 2018 [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%
Minimum Percentage Of Conversion Price Of Convertible Notes On 20 Of 30 Trading Days For The Options To Be Convertible	130.00%		130.00%
Debt Instrument, Convertible, Conversion Price	$ 69.03		$ 69.03
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, 130% of Conversion Price	$ 89.74		$ 89.74
Current convertible notes	188,413,000		188,413,000
Convertible notes conversion feature	61,587,000		61,587,000
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	170,885,000		170,885,000
Percentage Used As Debt Rate For Present Value Of Cash Flows	7.90%		7.90%
Debt Instrument, Convertible, Interest Expense	3,689,000	3,477,000	7,330,000	6,965,000
Interest accretion of convertible notes discount	2,439,000	2,227,000	4,830,000	4,465,000
Interest Expense, Debt, Excluding Amortization	1,250,000	1,250,000	2,500,000	2,500,000
Deferred Finance Costs, Gross	7,277,000		7,277,000
Financing costs amortization	178,000	177,000	355,000	355,000
Unamortized discount	61,587,000	66,417,000	61,587,000	66,417,000
Carrying amount of equity component	79,115,000		79,115,000
Senior Term Loan Due 2017 [Member] | Senior Credit Facility [Member]
Debt Instrument [Line Items]
Financing costs amortization	149,000	379,000	298,000	522,000
Additional Paid-in Capital [Member] | Convertible Notes Payable [Member] | Convertible Notes, Due 2018 [Member]
Debt Instrument [Line Items]
Deferred Finance Costs, Gross	2,303,000		2,303,000
Carrying Amount, Deferred Financing Fees [Member] | Convertible Notes Payable [Member] | Convertible Notes, Due 2018 [Member]
Debt Instrument [Line Items]
Deferred Finance Costs, Gross	$ 4,974,000		$ 4,974,000