Capital Stock (Cash Dividend Activity) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Dividends, Cash [Abstract]
Declaration Date	Oct. 27, 2015	Jul. 28, 2015	Apr. 28, 2015	Jan. 27, 2015	Oct. 28, 2014	Jul. 29, 2014	Apr. 29, 2014	Jan. 28, 2014
Record Date	Dec. 04, 2015	Sep. 10, 2015	Jun. 10, 2015	Mar. 10, 2015	Dec. 05, 2014	Sep. 10, 2014	Jun. 10, 2014	Mar. 10, 2014
Payment Date	Dec. 21, 2015	Sep. 25, 2015	Jun. 25, 2015	Mar. 25, 2015	Dec. 22, 2014	Sep. 25, 2014	Jun. 25, 2014	Mar. 25, 2014
Cash Dividend per Share	$ 0.6250	$ 0.6250	$ 0.6250	$ 0.6250	$ 0.4375	$ 0.4375	$ 0.4375	$ 0.4375
Total	$ 163.1	$ 163.0	$ 163.9	$ 166.6	$ 117.6	$ 119.2	$ 120.5	$ 123.4	$ 656.6	$ 480.7	$ 448.0