Commitments and Contingencies (Details) - October 2015 Share Repurchase Program - USD ($) $ / shares in Units, $ in Millions	1 Months Ended	2 Months Ended	6 Months Ended	12 Months Ended	20 Months Ended
	Jul. 21, 2017	Dec. 31, 2015	Jun. 30, 2017	Dec. 31, 2016	Jun. 30, 2017	Oct. 26, 2015
Stock Repurchases
Amount authorized under stock repurchase plan						$ 200.0
Share repurchases made in open market (in shares)	13,922	345,044	76,181	1,828,183	2,249,408
Average Price Paid per Share (in dollars per share)		$ 53.46	$ 70.54	$ 58.40
Aggregate Cost	$ 1.0	$ 18.4	$ 5.4	$ 106.8	$ 130.6