Statement of Consolidated Stockholders' Equity (USD $) In Millions, except Share data, unless otherwise specified	Total		Common Stock	Additional Paid in Capital	Retained Earnings	Common Stock Owned by Union VEBA	Treasury Stock	Accumulated Other Comprehensive Income (Loss)
Beginning balance at Dec. 31, 2010	$ 888.7		$ 0.2	$ 987.1	$ 78.0	$ (84.6)	$ (72.3)	$ (19.7)
Beginning balance, shares at Dec. 31, 2010			19,214,451
Stockholders' Equity [Roll Forward]
Net income	25.1				25.1
Other comprehensive income, net of tax	(65.3)							(65.3)
Release of restriction on Union VEBA shares, net of tax of $19.6, $25.0, and $41.3 for 2010, 2011, and 2012, respectively)	40.5			8.8		31.7
Issuance of non-vested shares to employees			83,066
Issuance of common shares to directors, shares			3,750
Issuance of common shares to directors	0.2			0.2
Issuance of common shares to employees upon vesting of restricted stock units and performance shares			17,444
Cancellation of employee non-vested shares			(2,889)
Cancellation of shares to cover employees’ tax withholdings upon vesting of non-vested shares, shares			(62,637)
Cancellation of shares to cover employees’ tax withholdings upon vesting of non-vested shares	(3.1)			(3.1)
Repurchase of common stock, shares	0
Shares returned from distribution of bankruptcy trust, value	0
Cash dividends on common stock ($0.96, $1.00 and $1.20 per share for 2011, 2012 and 2013, respectively)	(18.9)				(18.9)
Excess tax benefit upon vesting of non-vested shares and dividend payment on unvested shares expected to vest	0.2			0.2
Amortization of unearned equity compensation	5.2			5.2
Dividends on unvested equity awards that were canceled	0.2				0.2
Ending balance at Dec. 31, 2011	872.8		0.2	998.4	84.4	(52.9)	(72.3)	(85.0)
Ending balance, shares at Dec. 31, 2011			19,253,185
Stockholders' Equity [Roll Forward]
Net income	85.8				85.8
Other comprehensive income, net of tax	59.0							59.0
Release of restriction on Union VEBA shares, net of tax of $19.6, $25.0, and $41.3 for 2010, 2011, and 2012, respectively)	67.3			14.4		52.9
Issuance of non-vested shares to employees			92,949
Issuance of common shares to directors, shares			3,930
Issuance of common shares to directors	0.2			0.2
Issuance of common shares to employees upon vesting of restricted stock units and performance shares			11,327
Cancellation of employee non-vested shares			(2,355)
Cancellation of shares to cover employees’ tax withholdings upon vesting of non-vested shares, shares			(45,801)
Cancellation of shares to cover employees’ tax withholdings upon vesting of non-vested shares	(2.2)			(2.2)
Repurchase of common stock, shares	0
Shares returned from distribution of bankruptcy trust, value	0
Cash dividends on common stock ($0.96, $1.00 and $1.20 per share for 2011, 2012 and 2013, respectively)	(19.6)				(19.6)
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	5.6			5.6
Dividends on unvested equity awards that were canceled	0.6				0.6
Ending balance at Dec. 31, 2012	1,070.8		0.2	1,017.7	151.2	0	(72.3)	(26.0)
Ending balance, shares at Dec. 31, 2012	19,313,235		19,313,235
Stockholders' Equity [Roll Forward]
Net income	104.8				104.8
Other comprehensive income, net of tax	5.3							5.3
Issuance of non-vested shares to employees			76,336
Issuance of common shares to directors, shares			2,916
Issuance of common shares to directors	0.2			0.2
Issuance of common shares to employees upon vesting of restricted stock units and performance shares			36,503
Cancellation of employee non-vested shares			(820)
Cancellation of shares to cover employees’ tax withholdings upon vesting of non-vested shares, shares			(40,075)
Cancellation of shares to cover employees’ tax withholdings upon vesting of non-vested shares	(2.5)			(2.5)
Repurchase of common stock, shares	(1,232,077)		(1,232,077)
Repurchase of common stock	(79.3)						(79.3)
Shares returned from distribution of bankruptcy trust, shares			(9,001)
Dividends received from distribution of bankruptcy trust					0.6
Shares returned from distribution of bankruptcy trust, value	0.6	[1]					(0.6)
Cash dividends on common stock ($0.96, $1.00 and $1.20 per share for 2011, 2012 and 2013, respectively)	(23.0)				(23.0)
Excess tax benefit upon vesting of non-vested shares and dividend payment on unvested shares expected to vest	1.1			1.1
Amortization of unearned equity compensation	6.6			6.6
Dividends on unvested equity awards that were canceled	0.2				0.2
Ending balance at Dec. 31, 2013	$ 1,084.2		$ 0.2	$ 1,023.1	$ 233.8	$ 0	$ (152.2)	$ (20.7)
Ending balance, shares at Dec. 31, 2013	18,147,017		18,147,017

[1] See Note 13 for discussion of the distribution.