Indebtedness (Narrative) (Details)	9 Months Ended			3 Months Ended	9 Months Ended									9 Months Ended		9 Months Ended								9 Months Ended
	Sep. 30, 2014 USD ($)	Sep. 30, 2013 USD ($)	Dec. 31, 2013 USD ($)	Sep. 30, 2013 1 1/4% Convertible Senior Subordinated Notes Due December 15, 2036 [Member] USD ($)	Sep. 30, 2014 1 1/4% Convertible Senior Subordinated Notes Due December 15, 2036 [Member] USD ($)	Sep. 30, 2013 1 1/4% Convertible Senior Subordinated Notes Due December 15, 2036 [Member] USD ($)	Jun. 30, 2014 1 1/4% Convertible Senior Subordinated Notes Due December 15, 2036 [Member] USD ($)	Dec. 31, 2013 1 1/4% Convertible Senior Subordinated Notes Due December 15, 2036 [Member] USD ($)	Sep. 30, 2014 4 1/2% Senior Unsecured Term Loan Due 2016 [Member] USD ($)	Sep. 30, 2014 4 1/2% Senior Unsecured Term Loan Due 2016 [Member] EUR (€)	Dec. 31, 2013 4 1/2% Senior Unsecured Term Loan Due 2016 [Member] USD ($)	Sep. 30, 2014 5 7/8% Senior Notes due 2021 [Member] USD ($)	Dec. 31, 2013 5 7/8% Senior Notes due 2021 [Member] USD ($)	Sep. 30, 2014 5 7/8% Senior Notes due 2021 [Member] Interest Accrual, Option Two [Member]	Jun. 30, 2014 Revolving Credit Facility [Member] Line of Credit [Member] USD ($)	Sep. 30, 2014 Amended and Restated Credit Facility Agreement [Member] Line of Credit [Member] Interest Accrual, Option Two [Member]	Sep. 30, 2014 Amended and Restated Credit Facility Agreement [Member] Line of Credit [Member] Interest Accrual, Option Three [Member]	Sep. 30, 2014 Amended and Restated Credit Facility Agreement [Member] Line of Credit [Member] Minimum [Member] Interest Accrual, Option One [Member]	Sep. 30, 2014 Amended and Restated Credit Facility Agreement [Member] Line of Credit [Member] Minimum [Member] Interest Accrual, Option Three [Member] Variable Basis, Additional Margin [Member]	Sep. 30, 2014 Amended and Restated Credit Facility Agreement [Member] Line of Credit [Member] Maximum [Member] Interest Accrual, Option One [Member]	Sep. 30, 2014 Amended and Restated Credit Facility Agreement [Member] Line of Credit [Member] Maximum [Member] Interest Accrual, Option Three [Member] Variable Basis, Additional Margin [Member]	Sep. 30, 2014 Amended and Restated Credit Facility Agreement [Member] Term Loan Facility [Member] USD ($)	Sep. 30, 2014 Amended and Restated Credit Facility Agreement [Member] Revolving Credit Facility [Member] Line of Credit [Member] USD ($)	Sep. 30, 2014 Open Market Transaction [Member] USD ($)
Debt Instrument [Line Items]
Stock repurchased and retired during period	$ 340,900,000																							$ 50,900,000
Stock Repurchased and Retired During Period, Average Cost Per Share																								$ 48.46
Stock repurchased and retired during period, shares																								1,049,376
Carrying amount								54,300,000
Interest expense on the liability component of convertible debt				2,900,000	900,000	8,800,000
Debt instrument, interest rate, effective percentage					6.10%
Convertible senior subordinated notes conversion price (in dollars per share)							$ 40.27
Convertible senior subordinated notes, conversion rate					24.8295
Convertible senior subordinated notes, principal amount					1,000
Debt repurchased					49,700,000
Debt Conversion, Converted Instrument, Amount					151,500,000
Excess conversion value of notes					81,000,000
Debt Conversion, Converted Instrument, Amount	201,200,000	0
Shares issued					1,437,465
Days within trading period required to trigger qualifying event					20 days
Trading period in which qualifying event must occur					30 days
Senior notes									252,600,000		275,000,000	300,000,000	300,000,000
Debt Instrument, Face Amount									252,600,000	200,000,000.0		300,000,000.00
Margin on variable rate														0.50%		0.50%	1.00%	1.00%	0.00%	2.00%	0.50%
Maximum borrowing capacity on line of credit facility															600,000,000							355,000,000	800,000,000
Credit facility	735,000,000		360,000,000
Remaining borrowing capacity on line of credit facility	420,000,000		600,000,000
Long-term debt, estimated fair value								290,500,000				339,800,000	322,100,000
Convertible debt	0		201,200,000
Outstanding letters of credit	$ 18,700,000		$ 16,700,000