Stock Repurchase (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Stock Repurchase
Common stock repurchased (in shares)	1.3	0.7	0.8
Common stock repurchased, value	$ 18.7	$ 8.4	$ 11.7
Weighted average price per share of common stock (in dollars per share)	$ 14.98	$ 12.54	$ 14.40