Debt (Narrative) (Details) - Jun. 30, 2015 - USD ($) $ in Millions	Total	Total
Debt [Line Items]
Commercial paper, long-term	$ 111.2	$ 111.2
Senior Debentures [Member] | 3.3% senior debenture, due 2015 [Member]
Debt [Line Items]
Payments to retire long-term debt	$ 150.0
Interest rate	3.30%	3.30%
Commercial Paper [Member]
Debt [Line Items]
Interest rate	0.50%	0.50%
Weighted average remaining maturity, long-term debt (in days)		6 days