Financing Arrangements (Details 2) (USD $)			3 Months Ended			9 Months Ended				3 Months Ended	9 Months Ended
	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2013 Other borrowings	Sep. 30, 2013 1.5% Convertible Senior Notes due February 15, 2024	Sep. 30, 2012 1.5% Convertible Senior Notes due February 15, 2024	Sep. 30, 2013 1.5% Convertible Senior Notes due February 15, 2024	Sep. 30, 2012 1.5% Convertible Senior Notes due February 15, 2024	Dec. 31, 2012 1.5% Convertible Senior Notes due February 15, 2024	Feb. 29, 2004 1.5% Convertible Senior Notes due February 15, 2024	Mar. 31, 2013 5.625% Municipal Bonds	Sep. 30, 2013 5.625% Municipal Bonds	Dec. 31, 2012 5.625% Municipal Bonds
Financing Arrangements
Carrying value of the equity component				$ 19,519,000		$ 19,519,000		$ 19,519,000
Principal amount and carrying value of the liability component				18,398,000		18,398,000		18,472,000
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Conversion rate per $1,000 principal amount of Notes (in shares)						36.6729
Debt instrument, coupon interest				100,000	100,000	200,000	200,000
Debt instrument, convertible, if-converted value						48,000,000
Debt instrument interest rate (as a percent)				1.50%		1.50%		1.50%	1.50%			5.625%
Redemption price as a percentage of the principal amount (as a percent)										100.00%	100.00%
Borrowings under short-term credit facility			$ 7,000,000