Capital Stock (Summary of Cash Dividend Activity) (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2014	Mar. 31, 2014	Jun. 30, 2013	Mar. 31, 2013	Jun. 30, 2014	Jun. 30, 2013
Capital [Abstract]
Declaration date	Apr. 29, 2014	Jan. 28, 2014	May 15, 2013	Feb. 20, 2013
Record date	Jun. 10, 2014	Mar. 10, 2014	Jun. 10, 2013	Mar. 08, 2013
Payment date	Jun. 25, 2014	Mar. 25, 2014	Jun. 25, 2013	Mar. 25, 2013
Cash dividend per share	$ 0.4375	$ 0.4375	$ 0.3750	$ 0.3750	$ 0.8750	$ 0.7500
Total payment	$ 120.5	$ 123.4	$ 112.7	$ 113.4	$ 243.9	$ 226.1