Statement of Consolidated Stockholders' Equity - USD ($) $ in Millions	Total	Common Stock	Additional Paid In Capital	Retained Earnings	Treasury Stock	Accumulated Other Comprehensive (Loss) Income
Beginning balance, shares at Dec. 31, 2014		17,607,251
Beginning balance at Dec. 31, 2014	$ 1,015.9	$ 0.2	$ 1,028.5	$ 280.4	$ (197.1)	$ (96.1)
Stockholders' Equity [Roll Forward]
Net income (loss)	(236.6)			(236.6)
Other comprehensive income (loss), net of tax	64.4					64.4
Issuance of non-vested shares to employees		62,285
Issuance of common shares to non-employee directors	0.2		0.2
Issuance of common shares to directors, shares		2,436
Issuance of common shares to employees upon vesting of restricted stock units and performance shares, shares		52,106
Cancellation of employee non-vested shares, shares		(987)
Cancellation of shares to cover employees’ tax withholdings upon vesting of non-vested shares, shares		(37,009)
Cancellation of shares to cover employees’ tax withholdings upon vesting of non-vested shares	$ (2.8)		(2.8)
Repurchase of common stock, shares	(647,520)	(647,520)
Repurchase of common stock	$ (49.4)				(49.4)
Issuance of stock related to warrants, shares		1,015,185
Cash dividends on common stock	(28.1)			(28.1)
Excess tax benefit upon vesting of non-vested shares and dividend payment on unvested shares expected to vest	1.3		1.3
Amortization of unearned equity compensation	9.3		9.3
Dividends on unvested equity awards that were canceled	0.2			0.2
Ending balance, shares (Before Cumulative Adjustment) at Dec. 31, 2015		18,053,747
Ending balance (Before Cumulative Adjustment) at Dec. 31, 2015	774.4	$ 0.2	1,036.5	15.9	(246.5)	(31.7)
Ending balance at Dec. 31, 2015						(31.7)
Stockholders' Equity [Roll Forward]
Net income (loss)	91.7			91.7
Other comprehensive income (loss), net of tax	(5.0)					(5.0)
Issuance of non-vested shares to employees		9,702
Issuance of common shares to non-employee directors	0.1		0.1
Issuance of common shares to directors, shares		1,474
Issuance of common shares to employees upon vesting of restricted stock units and performance shares, shares		66,810
Issuance of common shares to employees upon option exercises and vesting of restricted stock units and performance shares	1.2		1.2
Cancellation of employee non-vested shares, shares		(379)
Cancellation of shares to cover employees’ tax withholdings upon vesting of non-vested shares, shares		(36,055)
Cancellation of shares to cover employees’ tax withholdings upon vesting of non-vested shares	$ (2.9)		(2.9)
Repurchase of common stock, shares	(443,838)	(443,838)
Repurchase of common stock	$ (34.9)				(34.9)
Cash dividends on common stock	(32.4)			(32.4)
Amortization of unearned equity compensation	11.7		11.7
Dividends on unvested equity awards that were canceled	$ 0.1			0.1
Ending balance, shares (Before Cumulative Adjustment) at Dec. 31, 2016		17,651,461
Ending balance, shares (Restatement Adjustment [Member])		18,053,747
Ending balance, shares at Dec. 31, 2016	17,651,461
Ending balance (Before Cumulative Adjustment) at Dec. 31, 2016	$ 804.7	$ 0.2	1,047.4	75.2	(281.4)	(36.7)
Ending balance (Restatement Adjustment [Member])	775.1	$ 0.2	1,037.3	15.8	(246.5)	(31.7)
Ending balance at Dec. 31, 2016	804.7					(36.7)
Cumulative Effect of New Accounting Principle in Period of Adoption	0.7		0.8	(0.1)
Stockholders' Equity [Roll Forward]
Net income (loss)	45.4			45.4
Issuance of non-vested shares to employees		11,817
Issuance of common shares to non-employee directors	0.2		0.2
Issuance of common shares to directors, shares		2,282
Issuance of common shares to employees upon vesting of restricted stock units and performance shares, shares		103,652
Issuance of common shares to employees upon vesting of restricted stock units and performance shares			0.0
Cancellation of employee non-vested shares, shares		(451)
Cancellation of shares to cover employees’ tax withholdings upon vesting of non-vested shares, shares		(56,495)
Cancellation of shares to cover employees’ tax withholdings upon vesting of non-vested shares	$ (4.5)		(4.5)
Repurchase of common stock, shares	(938,680)	(938,680)
Repurchase of common stock	$ (77.8)				(77.8)
Cancellation of treasury stock			(0.2)	(0.4)	0.6
Cash dividends on common stock	(35.0)			(35.0)
Amortization of unearned equity compensation	$ 13.0		13.0
Ending balance, shares at Dec. 31, 2017	16,773,586	16,773,586
Ending balance at Dec. 31, 2017	$ 746.3	$ 0.2	$ 1,055.9	85.5	$ (358.6)	$ (36.7)
Cumulative Effect of New Accounting Principle in Period of Adoption	$ 0.3			$ 0.3