Stockholders' Equity Stock Repurchases (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		6 Months Ended		51 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	May 23, 2016	Apr. 10, 2013
Equity, Class of Treasury Stock [Line Items]
Stock Repurchase Program, Remaining Authorized Repurchase Amount	$ 12.3		$ 12.3		$ 12.3
Treasury Stock Acquired, Average Cost Per Share	$ 17.22	$ 16.62	$ 17.16	$ 16.62
Stock Repurchased During Period, Value	$ 8.2	$ 1.4	$ 13.3	$ 1.4	$ 27.7
Stock Repurchased and Retired During Period, Shares	478,147	85,537	775,370	85,537	1,640,012
May 2016 Repurchase Program [Member]
Equity, Class of Treasury Stock [Line Items]
Stock Repurchase Program, Authorized Amount						$ 20.0
April 2013 Repurchase Program [Member]
Equity, Class of Treasury Stock [Line Items]
Stock Repurchase Program, Authorized Amount							$ 20.0