Consolidated Statements of Stockholders' Equity - USD ($) shares in Millions, $ in Millions	Common Stock	Additional Paid In Capital	Accumulated Other Comprehensive Income (Loss)	Retained Earnings	Total
Balance at the beginning of the period at Dec. 31, 2013	$ 32.1	$ 261.9	$ (23.5)	$ 67.7	$ 338.2
Balance (in shares) at Dec. 31, 2013	42.8
Increase (Decrease) in Stockholders' Equity
Net income				70.8	70.8
Other comprehensive income (loss), net of tax			(29.8)		(29.8)
Excess tax benefit and share withholding		0.8			0.8
Share-based compensation		8.7			8.7
Shares issued	$ 0.3	3.5			3.8
Shares issued (in shares)	0.4
Dividends ($0.74, $0.70, and $0.66 per share) for the years 2016, 2015 and 2014 respectively				(28.7)	(28.7)
Balance at the end of the period at Dec. 31, 2014	$ 32.4	274.9	(53.3)	109.8	363.8
Balance (in shares) at Dec. 31, 2014	43.2
Increase (Decrease) in Stockholders' Equity
Net income				103.0	103.0
Other comprehensive income (loss), net of tax			6.4		6.4
Excess tax benefit and share withholding		2.6			2.6
Share-based compensation		12.2			12.2
Shares issued	$ 0.3	(1.0)			(0.7)
Shares issued (in shares)	0.4
Shares repurchased	$ (0.1)	(0.8)		(5.0)	(5.9)
Shares repurchased (in shares)	(0.1)
Dividends ($0.74, $0.70, and $0.66 per share) for the years 2016, 2015 and 2014 respectively				(30.8)	(30.8)
Balance at the end of the period at Dec. 31, 2015	$ 32.6	287.9	(46.9)	177.0	$ 450.6
Balance (in shares) at Dec. 31, 2015	43.5				43.5
Increase (Decrease) in Stockholders' Equity
Net income				80.5	$ 80.5
Other comprehensive income (loss), net of tax			0.8		0.8
Excess tax benefit and share withholding		2.2			2.2
Share-based compensation		11.2			11.2
Shares issued	$ 0.2	(4.9)			(4.7)
Shares issued (in shares)	0.3
Shares repurchased	$ (0.7)	(6.6)		(29.6)	(36.9)
Shares repurchased (in shares)	(0.9)
Dividends ($0.74, $0.70, and $0.66 per share) for the years 2016, 2015 and 2014 respectively				(32.2)	(32.2)
Balance at the end of the period at Dec. 31, 2016	$ 32.1	$ 289.8	$ (46.1)	$ 195.7	$ 471.5
Balance (in shares) at Dec. 31, 2016	42.9				42.9