Debt (Textuals) (Details)	12 Months Ended								12 Months Ended		12 Months Ended		12 Months Ended				12 Months Ended			12 Months Ended
	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Dec. 31, 2012 USD ($)	Dec. 31, 2014 Senior A Notes Due 2022 [Member]	Dec. 31, 2014 Senior B Notes Due 2024 [Member]	Dec. 31, 2014 Senior C Notes Due 2027 [Member]	Dec. 31, 2014 Revolving Credit Facility Due 2017 [Member] USD ($)	Dec. 31, 2013 Revolving Credit Facility Due 2017 [Member] USD ($)	Dec. 31, 2014 Term Loan Due 2018 [Member] USD ($)	Dec. 31, 2013 Term Loan Due 2018 [Member] USD ($)	Dec. 31, 2014 Series B Floating Rate Notes Due 2015 [Member] USD ($)	Dec. 31, 2013 Series B Floating Rate Notes Due 2015 [Member] USD ($)	Dec. 31, 2014 EURO Note B Due 2016 [Member] USD ($)	Dec. 31, 2014 EURO Note B Due 2016 [Member] EUR (€)	Dec. 31, 2013 EURO Note B Due 2016 [Member] USD ($)	Dec. 31, 2011 Convertible Debt Due 2047 [Member] USD ($)	Dec. 31, 2013 Convertible Debt Due 2047 [Member] USD ($)	Dec. 31, 2012 Convertible Debt Due 2047 [Member] USD ($)	Dec. 31, 2014 Convertible Debt Due 2047 [Member] USD ($)	Dec. 31, 2014 Senior Notes [Member] USD ($)	Dec. 31, 2014 Senior Notes [Member] Senior A Notes Due 2022 [Member] USD ($)	Dec. 31, 2013 Senior Notes [Member] Senior A Notes Due 2022 [Member] USD ($)	Dec. 31, 2014 Senior Notes [Member] Senior B Notes Due 2024 [Member] USD ($)	Dec. 31, 2013 Senior Notes [Member] Senior B Notes Due 2024 [Member] USD ($)	Dec. 31, 2014 Senior Notes [Member] Senior C Notes Due 2027 [Member] USD ($)	Dec. 31, 2013 Senior Notes [Member] Senior C Notes Due 2027 [Member] USD ($)	Dec. 31, 2014 Letter of Credit [Member] Revolving Credit Facility Due 2017 [Member] USD ($)
Line of Credit Facility [Line Items]
Losses on Extinguishment of Debt	$ 0	$ 200,000	$ 11,600,000														$ 200,000	$ 11,600,000
Gains (Losses) on extinguishment of debt, less than	(100,000)
Line of Credit Facility, expiration date							Apr. 30, 2017
Line of Credit Facility, current borrowing capacity							300,000,000.0
Line of Credit Facility, maximum borrowing capacity							350,000,000.0
Credit facility is available for swing-line loans							30,000,000.0
Credit available for the issuance of letters of credit							30,000,000.0
Line of credit interest rate margin added to Libor at minimum (in hundredths)							1.25
Line of credit interest rate margin added to Libor at maximum (in hundredths)							2.25
Debt issuance cost							2,400,000													1,200,000
Long-term debt	336,700,000	373,500,000					29,700,000	53,700,000	39,200,000	41,300,000	25,000,000	25,000,000	74,300,000		84,100,000		600,000			168,000,000	42,000,000	42,000,000	53,000,000	53,000,000	73,000,000	73,000,000
Long-term Debt, Current Maturities									2,100,000
Line of credit facility outstanding borrowings, Yen							4,200,000
Line of credit facility outstanding borrowings, Euro							25,500,000
Line of Credit, noncurrent								53,700,000
Outstanding amount																											3,500,000
Line of Credit Facility, unused commitment level							266,800,000
Term of debt													10 years	10 years
Variable rate basis							LIBOR		LIBOR		LIBOR
Basis spread on variable interest rate									1.50%		0.90%
Debt Instrument, face amount									42,800,000					61,100,000
Debt Instrument, Term									5 years
Debt instrument, maturity date				Jul. 05, 2022	Jul. 05, 2024	Jul. 05, 2027			Jan. 31, 2018		Jul. 28, 2015		Feb. 27, 2016	Feb. 27, 2016
Debt instrument, stated interest rate				3.67%	3.82%	4.02%	1.71%		1.66%		1.13%		4.38%	4.38%					4.00%		3.67%		3.82%		4.02%
Long-term debt, excluding current portion	309,500,000	371,300,000														161,500,000
Debt instrument, repurchase amount																	2,500,000	158,400,000	600,000
Percentage of convertible debt repurchased																	98.06%
Weighted average of the coupon interest rate																				3.87%
Annual effective interest rate																				4.16%
Interest expense	18,100,000	18,600,000	18,600,000
Aggregate annual maturities of long-term debt [Abstract]
2015	27,200,000
2016	76,800,000
2017	32,100,000
2018	32,600,000
Thereafter	$ 168,000,000