Stockholders' Equity - Share Repurchase Program (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Class of Stock [Line Items]
Common stock repurchased and retired, shares	1,987,187	2,326,493
Common stock repurchased and retired, weighted average price per share	$ 50.49	$ 66.50
Common stock repurchased and retired, total value	$ 100.3	$ 154.7
Common stock repurchase authorization amount available	$ 193.0