Stockholders' Equity (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	0 Months Ended	3 Months Ended			0 Months Ended
	Feb. 26, 2015	Mar. 31, 2015	Mar. 31, 2014	Jun. 30, 2015	May 15, 2013
Common stock dividends paid		$ 39.4	$ 39.3
Dividends declared per common share	$ 0.55	$ 0.55	$ 0.40
Subsequent Event
Common stock dividends paid				$ 54.1
Annual Dividend
Dividends declared per common share	$ 2.20				$ 1.60