Equity (Details) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended			9 Months Ended
	Aug. 31, 2015	Sep. 30, 2015	Mar. 31, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Equity [Abstract]
Stock repurchased (in shares)					4,885,077
Common stock issued under stock compensation plan (in shares)					1,875,967
Net decrease in period (in shares)					3,009,110
Increase in quarterly cash dividend rate (in dollars per share)		$ 0.005
Dividends declared (in dollars per share)		$ 0.085	$ 0.08	$ 0.08	$ 0.25	$ 0.23
Dividends declared	$ 24.8