Shareholders' Equity (Details) - USD ($) shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Shareholders' Equity [Abstract]
Common stock repurchased during the period (in shares)	1.0	1.8	1.9	2.0
Common stock repurchased during the period, value	$ 66.3	$ 97.8	$ 127.2	$ 108.8