Condensed Balance Sheets Parenthetical (USD $) In Millions, except Per Share data, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2013
ASSETS
Accumulated depreciation	$ 1,324.6	$ 1,259.1	$ 1,236.8
Shareholders' equity:
Common stock, par value	$ 1.00	$ 1.00	$ 1.00
Common stock, authorized	120.0	120.0	120.0
Common stock, issued	78.2	79.4	79.6
Common stock, outstanding	78.2	79.4	79.6