Guarantor and Non-Guarantor Financial Statements (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended				3 Months Ended		6 Months Ended				3 Months Ended		6 Months Ended				3 Months Ended		6 Months Ended				3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012		Dec. 31, 2012	Jun. 30, 2013 Parent	Jun. 30, 2012 Parent	Jun. 30, 2013 Parent	Jun. 30, 2012 Parent		Dec. 31, 2012 Parent	Jun. 30, 2013 Guarantor Subsidiaries	Jun. 30, 2012 Guarantor Subsidiaries	Jun. 30, 2013 Guarantor Subsidiaries	Jun. 30, 2012 Guarantor Subsidiaries		Dec. 31, 2012 Guarantor Subsidiaries	Jun. 30, 2013 Non-Guarantor Subsidiaries	Jun. 30, 2012 Non-Guarantor Subsidiaries	Jun. 30, 2013 Non-Guarantor Subsidiaries	Jun. 30, 2012 Non-Guarantor Subsidiaries		Dec. 31, 2012 Non-Guarantor Subsidiaries	Jun. 30, 2013 Consolidating Adjustments	Jun. 30, 2012 Consolidating Adjustments	Jun. 30, 2013 Consolidating Adjustments	Jun. 30, 2012 Consolidating Adjustments		Dec. 31, 2012 Consolidating Adjustments	May 23, 2012 Senior Notes
Condensed Financial Statements [Line Items]
Principal amount of notes	$ 225.0		$ 225.0			$ 225.0																									$ 225.0
Ownership interest by parent	100.00%		100.00%
Current assets:
Cash and cash equivalents	281.7	317.8	281.7	317.8			5.0	5.0	5.0	5.0			275.7	311.9	275.7	311.9			1.0	0.9	1.0	0.9			0	0	0	0
Short-term investments	47.3		47.3			85.0	0		0			0	47.3		47.3			85.0	0		0			0	0		0			0
Receivables:
Trade, less allowance for doubtful receivables	122.7		122.7			123.8	0		0			0	120.0		120.0			121.5	2.7		2.7			2.3	0		0			0
Intercompany receivables	0		0			0	0		0			0	0.1		0.1			(10.3)	0.4		0.4			0.4	(0.5)		(0.5)			9.9
Other	11.6		11.6			3.4	0		0			0	1.5		1.5			1.3	10.1		10.1			2.1	0		0			0
Inventories	202.9		202.9			186.0	0		0			0	195.4		195.4			178.7	8.0		8.0			7.3	(0.5)		(0.5)			0
Prepaid expenses and other current assets	70.1		70.1			70.1	0		0			0	68.2		68.2			68.1	1.9		1.9			2.0	0		0			0
Total current assets	736.3		736.3			741.7	5.0		5.0			5.0	708.2		708.2			710.3	24.1		24.1			16.5	(1.0)		(1.0)			9.9
Investments in and advances to unconsolidated affiliates	0		0			0	1,364.1		1,364.1			1,284.1	16.3		16.3			7.4	0		0			0	(1,380.4)		(1,380.4)			(1,291.5)
Property, plant, and equipment – net	398.3		398.3			384.3	0		0			0	385.3		385.3			371.8	13.0		13.0			12.5	0		0			0
Long-term intercompany receivables	0		0			0	95.6		95.6			163.7	1.3		1.3			0.4	10.5		10.5			6.4	(107.4)		(107.4)			(170.5)
Net asset in respect of VEBA	379.1		379.1			365.9	0		0			0	379.1		379.1			365.9	0		0			0	0		0			0
Deferred tax assets (liabilities) — net	75.8		75.8			102.0	0		0			0	67.5		67.5			93.4	(1.0)		(1.0)			(0.8)	9.3		9.3			9.4
Intangible assets – net	34.5		34.5			35.4	0		0			0	34.5		34.5			35.4	0		0			0	0		0			0
Goodwill	37.2		37.2			37.2	0		0			0	37.2		37.2			37.2	0		0			0	0		0			0
Other assets	78.5		78.5			86.0	59.9		59.9			64.0	18.5		18.5			19.2	0.1		0.1			3.0	0		0			(0.2)
Total	1,739.7		1,739.7			1,752.5	1,524.6		1,524.6			1,516.8	1,647.9		1,647.9			1,641.0	46.7		46.7			37.6	(1,479.5)		(1,479.5)			(1,442.9)
Current liabilities:
Accounts payable	73.2		73.2			62.5	0.5		0.5			0.1	64.3		64.3			56.5	8.4		8.4			5.9	0		0			0
Intercompany payable	0		0			0	0		0			0	7.5		7.5			0.3	0.2		0.2			0.2	(7.7)		(7.7)			(0.5)
Accrued salaries, wages, and related expenses	33.7		33.7			39.3	0		0			0	30.5		30.5			36.7	3.2		3.2			2.6	0		0			0
Other accrued liabilities	39.9		39.9			51.8	3.5		3.5			3.5	35.3		35.3			47.8	1.1		1.1			0.5	0		0			0
Payable to affiliate	0		0			7.9						0						7.9						0						0
Short-term capital lease	0.3		0.3			0.1	0		0			0	0.3		0.3			0.1	0		0			0	0		0			0
Total current liabilities	147.1		147.1			161.6	4.0		4.0			3.6	137.9		137.9			149.3	12.9		12.9			9.2	(7.7)		(7.7)			(0.5)
Net liability in respect of VEBA	4.5		4.5			5.3	0		0			0	4.5		4.5			5.3	0		0			0	0		0			0
Long-term intercompany payable	0		0			0	0		0			0	106.1		106.1			170.0	1.3		1.3			0.5	(107.4)		(107.4)			(170.5)
Long-term liabilities	127.0		127.0			134.5	59.5		59.5			62.1	48.9		48.9			49.6	18.6		18.6			22.8	0		0			0
Long-term debt	384.3		384.3			380.3	384.3		384.3			380.3	0		0			0	0		0			0	0		0			0
Total liabilities	662.9		662.9			681.7	447.8		447.8			446.0	297.4		297.4			374.2	32.8		32.8			32.5	(115.1)		(115.1)			(171.0)
Total stockholders’ equity	1,076.8		1,076.8			1,070.8	1,076.8		1,076.8			1,070.8	1,350.5		1,350.5			1,266.8	13.9		13.9			5.1	(1,364.4)		(1,364.4)			(1,271.9)
Total	1,739.7		1,739.7			1,752.5	1,524.6		1,524.6			1,516.8	1,647.9		1,647.9			1,641.0	46.7		46.7			37.6	(1,479.5)		(1,479.5)			(1,442.9)
CONDENSED CONSOLIDATING STATEMENT OF COMPREHENSIVE INCOME
Net sales	328.9	345.2	666.3	710.6			0	0	0	0			324.7	335.0	656.5	690.5			29.6	32.1	60.0	64.7			(25.4)	(21.9)	(50.2)	(44.6)
Cost of products sold:
Cost of products sold, excluding depreciation and amortization and other items	261.5	284.4	525.1	582.5			0	0	0	0			258.9	276.8	518.6	567.3			26.3	29.0	53.3	58.9			(23.7)	(21.4)	(46.8)	(43.7)
Unrealized losses (gains) on derivative instruments	4.2	0.1	4.9	(3.0)			0	0	0	0			4.2	0.1	4.9	(3.0)			0	0	0	0			0	0	0	0
Depreciation and amortization	7.0	6.6	14.0	12.9			0	0	0	0			6.8	6.3	13.5	12.4			0.2	0.3	0.5	0.5			0	0	0	0
Selling, administrative, research and development, and general	16.1	14.4	32.2	32.3			1.1	0.8	1.5	1.3			14.5	13.5	29.3	31.2			2.1	0.7	4.5	0.7			(1.6)	(0.6)	(3.1)	(0.9)
Other operating charges, net		0.1		0.1				0		0				0.1		0.1				0		0				0		0
Total costs and expenses	288.8	305.6	576.2	624.8			1.1	0.8	1.5	1.3			284.4	296.8	566.3	608.0			28.6	30.0	58.3	60.1			(25.3)	(22.0)	(49.9)	(44.6)
Operating (loss) income	40.1	39.6	90.1	85.8			(1.1)	(0.8)	(1.5)	(1.3)			40.3	38.2	90.2	82.5			1.0	2.1	1.7	4.6			(0.1)	0.1	(0.3)	0
Other (expense) income:
Interest expense	(9.0)	(6.5)	(18.3)	(10.6)			(9.0)	(6.2)	(18.1)	(10.2)			0	(0.3)	(0.3)	(0.4)			0	0	0	0			0	0	0.1	0
Other income, net	(0.8)	1.1	0.2	1.8			(0.9)	0.7	(0.5)	1.2			0.3	0.3	0.9	0.5			(0.2)	0.1	(0.1)	0.1			0	0	(0.1)	0
(Loss) income before income taxes	30.3	34.2	72.0	77.0			(11.0)	(6.3)	(20.1)	(10.3)			40.6	38.2	90.8	82.6			0.8	2.2	1.6	4.7			(0.1)	0.1	(0.3)	0
Income tax (provision) benefit	(11.7)	(13.2)	(19.9)	(29.5)			0	0	0	0			(15.1)	(14.7)	(34.1)	(31.5)			(0.7)	(0.7)	6.5	(1.4)			4.1	2.2	7.7	3.4
Earnings in equity of subsidiaries	0	0	0	0			29.6	27.3	72.2	57.8			(0.1)	1.6	7.7	3.3			0	0	0	0			(29.5)	(28.9)	(79.9)	(61.1)
Net income	18.6	21.0	52.1	47.5			18.6	21.0	52.1	47.5			25.4	25.1	64.4	54.4			0.1	1.5	8.1	3.3			(25.5)	(26.6)	(72.5)	(57.7)
Comprehensive income	19.9	22.5	54.6	50.1			19.9	22.5	54.6	50.1			26.3	26.2	66.1	56.9			0.5	1.9	8.9	3.4			(26.8)	(28.1)	(75.0)	(60.3)
Cash flows from operating activities:
Net cash (used in) provided by operating activities			48.9	74.7					(14.4)	(3.5)					60.4	78.5					2.9	(0.3)					0	0
Cash flows from investing activities:
Capital expenditures	(16.7)	(7.9)	(26.0)	(16.9)					0	0					(25.0)	(16.4)					(1.0)	(0.5)					0	0
Purchase of available for sale securities			(98.2)	(0.3)					0	0					(98.2)	(0.3)					0	0					0	0
Proceeds from sale of available for sale securities			135.7	0					0						135.7						0						0
Change in restricted cash			0.7	7.2					0	6.9					0.7	0.3					0	0					0	0
Net cash provided by (used in) investing activities			12.2	(10.0)					0	6.9					13.2	(16.4)					(1.0)	(0.5)					0	0
Cash flows from financing activities:
Proceeds from issuance of senior notes			0	225.0						225.0						0						0						0
Cash paid for financing costs			0	(6.4)						(6.4)						0						0						0
Repayment of promissory notes			0	(4.7)						0						(4.7)						0						0
Excess tax benefit upon vesting of non-vested shares and dividend payment on unvested shares expected to vest			0.9	1.3					0	0					0.9	1.3					0	0					0	0
Cancellation of shares to cover employees’ tax withholdings upon vesting of non-vested shares			(2.2)	(2.1)					(2.2)	(2.1)					0	0					0	0					0	0
Cash dividend paid to stockholders			(11.6)	(9.8)					(11.6)	(9.8)					0	0					0	0					0	0
Repurchase of common stock			(39.9)	0					(39.9)						0						0						0
Intercompany loan			0	0	[1]				68.1	(210.1)	[1]				(64.8)	210.2	[1]				(3.3)	(0.1)	[1]				0	0	[1]
Net cash provided by (used in) financing activities			(52.8)	203.3					14.4	(3.4)					(63.9)	206.8					(3.3)	(0.1)					0	0
Net increase (decrease) in cash and cash equivalents during the period			8.3	268.0					0	0					9.7	268.9					(1.4)	(0.9)					0	0
Cash and cash equivalents at beginning of period			273.4	49.8					5.0	5.0					266.0	43.0					2.4	1.8					0	0
Cash and cash equivalents at end of period	$ 281.7	$ 317.8	$ 281.7	$ 317.8			$ 5.0	$ 5.0	$ 5.0	$ 5.0			$ 275.7	$ 311.9	$ 275.7	$ 311.9			$ 1.0	$ 0.9	$ 1.0	$ 0.9			$ 0	$ 0	$ 0	$ 0

[1] The Company treats changes in long-term intercompany balances that relate to financing activities as cash flow from financing activities. In the above table, the Company has corrected the previous classification of the changes in such intercompany balances during six months ended June 30, 2012 from cash flows from operating activities to a separate line item in cash flows from financing activities captioned “intercompany loan”. Management has concluded that the correction of these errors is immaterial.