Commitments and Contingencies (Details) (October 2014 Share Repurchase Program, USD $) In Millions, except Share data, unless otherwise specified	1 Months Ended		3 Months Ended	4 Months Ended
	Apr. 27, 2015	Dec. 31, 2014	Mar. 31, 2015	Mar. 31, 2015	Oct. 22, 2014
October 2014 Share Repurchase Program
Stock Repurchases
Amount authorized under stock repurchase plan					$ 200
Share repurchases made in open market (in shares)	101,547	232,170	509,935	742,105
Average Price Paid per Share (in dollars per share)		$ 60.65	$ 62.14
Aggregate Cost	$ 7.2	$ 14.1	$ 31.7	$ 45.8