Long-Term Debt (Details) (USD $)	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Debt Instrument Issuance [Abstract]
Settlement of Foreign Currency Swap	$ (31,573,000)	$ 0
Settlement of Interest Rate Swap	800,000
Line of Credit Facility [Line Items]
Quarterly Dividends, Common Stock, Cash	0.125	0.09375
Uncommitted Credit Facility [Member]
Line of Credit Facility [Line Items]
Average Borrowings Outstanding	300,000	0
Weighted average interest rate (in hundredths)	0.70%
Commercial Paper [Member]
Line of Credit Facility [Line Items]
Average Borrowings Outstanding	31,000,000	2,000,000
Weighted average interest rate (in hundredths)	0.25%	0.36%
Revolving Credit Agreement [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Expiration Date	Oct. 11, 2016
Maximum borrowing capacity	2,000,000
Eurodollar rate at period end (in hundredths)	1.03%
Base rate at period end (in hundredths)	3.25%
Floating Rate Senior Notes Due 2014 [Member]
Debt Instrument Issuance [Abstract]
Debt Instrument Issuance Face Amount	350,000,000
4.75% Subsidiary Debt Due 2014 [Member]
Debt Instrument Issuance [Abstract]
Debt Instrument Issuance Face Amount	150,000,000
Debt Instrument Issuance Interest Rate	4.75%
2.45% Senior Notes Due 2020 [Member]
Debt Instrument Issuance [Abstract]
Debt Instrument Issuance Face Amount	500,000,000
Debt Instrument Issuance Interest Rate	2.45%
Proceeds from Issuance of Senior Long-Term Debt	$ 496,000,000