Debt (Textuals) (Details)	12 Months Ended						3 Months Ended				12 Months Ended		12 Months Ended		12 Months Ended		12 Months Ended			12 Months Ended
	Dec. 31, 2013 USD ($)	Dec. 31, 2012 USD ($)	Dec. 31, 2011 USD ($)	Dec. 31, 2013 Senior A Notes Due 2022 [Member]	Dec. 31, 2013 Senior B Notes Due 2024 [Member]	Dec. 31, 2013 Senior C Notes Due 2027 [Member]	Jun. 30, 2012 Revolving Credit Facility Due 2014 [Member] USD ($)	Jun. 30, 2012 Revolving Credit Facility Due 2017 [Member] USD ($)	Dec. 31, 2013 Revolving Credit Facility Due 2017 [Member] USD ($)	Dec. 31, 2012 Revolving Credit Facility Due 2017 [Member] USD ($)	Dec. 31, 2013 Term Loan Due 2018 [Member] USD ($)	Dec. 31, 2012 Term Loan Due 2018 [Member] USD ($)	Dec. 31, 2013 Series B Floating Rate Notes Due 2015 [Member] USD ($)	Dec. 31, 2012 Series B Floating Rate Notes Due 2015 [Member] USD ($)	Dec. 31, 2013 EURO Note A Due 2013 [Member] USD ($)	Dec. 31, 2012 EURO Note A Due 2013 [Member] USD ($)	Dec. 31, 2013 EURO Note B Due 2016 [Member] USD ($)	Dec. 31, 2013 EURO Note B Due 2016 [Member] EUR (€)	Dec. 31, 2012 EURO Note B Due 2016 [Member] USD ($)	Dec. 31, 2013 Convertible Debt Due 2047 [Member] USD ($)	Dec. 31, 2013 Convertible Debt Due 2047 [Member] USD ($)	Dec. 31, 2012 Convertible Debt Due 2047 [Member] USD ($)	Dec. 31, 2013 Senior Notes [Member] USD ($)	Dec. 31, 2013 Senior Notes [Member] Senior A Notes Due 2022 [Member] USD ($)	Dec. 31, 2012 Senior Notes [Member] Senior A Notes Due 2022 [Member] USD ($)	Dec. 31, 2013 Senior Notes [Member] Senior B Notes Due 2024 [Member] USD ($)	Dec. 31, 2012 Senior Notes [Member] Senior B Notes Due 2024 [Member] USD ($)	Dec. 31, 2013 Senior Notes [Member] Senior C Notes Due 2027 [Member] USD ($)	Dec. 31, 2012 Senior Notes [Member] Senior C Notes Due 2027 [Member] USD ($)	Dec. 31, 2013 Letter of Credit [Member] Revolving Credit Facility Due 2017 [Member] USD ($)
Line of Credit Facility [Line Items]
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							800,000	1,600,000															1,200,000
Long-term debt	373,500,000	411,500,000							53,700,000	71,500,000	41,300,000	35,300,000		25,000,000		26,900,000	84,100,000		80,800,000		600,000	3,100,000	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											2,000,000
Line of credit facility outstanding borrowings, Yen									4,800,000
Line of credit facility outstanding borrowings, Euro									28,900,000
Line of Credit, current									5,700,000
Line of Credit, noncurrent									65,800,000
Outstanding amount																														3,500,000
Line of Credit Facility, unused commitment level									242,800,000
Term of debt																	10 years	10 years
Variable rate basis											LIBOR		LIBOR
Basis spread on variable interest rate											1.50%		0.90%
Debt Instrument, face amount											42,800,000		25,000,000					61,100,000
Debt Instrument, Term											5 years
Debt instrument, maturity date													Jul. 28, 2015		Feb. 27, 2013		Feb. 27, 2016	Feb. 27, 2016		Mar. 15, 2047	Mar. 15, 2047
Debt instrument, stated interest rate				3.67%	3.82%	4.02%			1.68%		1.67%		1.14%		4.215%		4.38%	4.38%		4.00%	4.00%			3.67%		3.82%		4.02%
Long-term debt	371,300,000	378,800,000																		161,500,000
Conversion ratio of debt per $1,000 of debt																				36.3777	36.3777
Convertbile debt, conversion price (in usd per share)																				$ 27.49
Debentures automatic conversion feature																				Subsequent to March 20, 2012, if our common stock closing price exceeds 150% of the then prevailing conversion price for at least 20 trading days during any 30 consecutive trading day period, we have the option to cause the debentures to be automatically converted into West shares at the prevailing conversion rate	Subsequent to March 20, 2012, if our common stock closing price exceeds 150% of the then prevailing conversion price for at least 20 trading days during any 30 consecutive trading day period, we have the option to cause the debentures to be automatically converted into West shares at the prevailing conversion rate
Debt instrument, repurchase amount																					2,500,000	158,400,000
Percentage of convertible debt repurchased																						98.06%
Loss on debt extinguishment																					200,000	11,600,000
Weighted average of the coupon interest rate																							3.87%
Annual effective interest rate																							4.16%
Interest expense	18,600,000	18,600,000	19,300,000
Aggregate annual maturities of long-term debt [Abstract]
2014	27,200,000
2015	86,800,000
2016	56,100,000
2017	32,500,000
2018	100,000
Thereafter	$ 168,600,000