Statement of Consolidated Stockholders' Equity (USD $) In Millions, except Share data, unless otherwise specified	Total	Common Stock	Additional Paid in Capital	Retained Earnings	Treasury Stock	Accumulated Other Comprehensive Loss
Beginning balance at Dec. 31, 2013	$ 1,084.2	$ 0.2	$ 1,023.1	$ 233.8	$ (152.2)	$ (20.7)
Beginning balance, shares at Dec. 31, 2013	18,147,017	18,147,017
Stockholders' Equity [Roll Forward]
Net income	15.8			15.8
Other comprehensive income, net of tax	0.9					0.9
Issuance of non-vested shares to employees, shares		55,613
Issuance of common shares to employees upon vesting of restricted stock units and performance shares, shares		43,562
Cancellation of employee non-vested shares		(323)
Cancellation of shares to cover employees’ tax withholdings upon vesting of non-vested shares, shares		(30,869)
Cancellation of shares to cover employees’ tax withholdings upon vesting of non-vested shares	(2.2)		(2.2)
Repurchase of common stock, shares	(184,400)	(184,400)
Repurchase of common stock	(12.7)				(12.7)
Cash dividends on common stock ($0.35 per share)	(6.4)			(6.4)
Excess tax benefit upon vesting of non-vested shares and dividend payment on unvested shares expected to vest	0.7		0.7
Amortization of unearned equity compensation	2.0		2.0
Ending balance at Mar. 31, 2014	$ 1,082.3	$ 0.2	$ 1,023.6	$ 243.2	$ (164.9)	$ (19.8)
Ending balance, shares at Mar. 31, 2014	18,030,600	18,030,600