Stockholders' Equity - Share Repurchase Program (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended	6 Months Ended	24 Months Ended
	Jun. 30, 2016	Jun. 30, 2016	Jun. 30, 2016	Oct. 31, 2015
Stockholders' Equity Note [Abstract]
Amount of shares authorized to be repurchased				$ 335.0
Shares repurchased	882,808	4,999,079	13,961,865
Cost of shares repurchased	$ 15.9	$ 76.8	$ 296.4
Average purchase price	$ 18.00	$ 15.37	$ 21.23