Stockholders' Equity (Details) - USD ($) $ / shares in Units, $ in Millions						3 Months Ended		6 Months Ended
	Aug. 09, 2016	Jun. 15, 2016	May 09, 2016	Mar. 28, 2016	Feb. 24, 2016	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Dividends Payable [Line Items]
Dividends per share (in dollars per share)			$ 0.08		$ 0.08	$ 0.08	$ 0.065	$ 0.16	$ 0.13
Cash payment amount		$ 3.7		$ 3.8				$ 7.5	$ 6.1
Common stock available for future share repurchases, amount						$ 8.0		$ 8.0
Common stock repurchased, number of shares repurchased						43,682	100,032	88,916	197,816
Common stock repurchased, average price per share (in dollars per share)						$ 40.05	$ 29.97	$ 39.36	$ 30.32
Common stock repurchased, total repurchase costs						$ 1.7	$ 3.0	$ 3.5	$ 6.0
Subsequent Event
Dividends Payable [Line Items]
Dividends per share (in dollars per share)	$ 0.08