Debt (Details) (USD $)	Mar. 31, 2013	Dec. 31, 2012
Debt Disclosure [Abstract]
Notional Amount of Interest Rate Fair Value Hedge Derivatives	$ 300,000,000	$ 550,000,000
Short-term debt and current portion of long-term debt:
Short-term debt, Weighted Average Interest Rate	1.49%	2.27%
Short-term debt	2,015,000	9,820,000
Current portion of long-term debt, including capital leases	257,718,000	358,155,000
Total short-term debt and current portion of long-term debt	$ 259,733,000	$ 367,975,000