Guarantor and Non-Guarantor Financial Statements (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended				3 Months Ended		9 Months Ended				3 Months Ended		9 Months Ended				3 Months Ended		9 Months Ended				3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012		Dec. 31, 2012	Sep. 30, 2013 Parent	Sep. 30, 2012 Parent	Sep. 30, 2013 Parent	Sep. 30, 2012 Parent		Dec. 31, 2012 Parent	Sep. 30, 2013 Guarantor Subsidiaries	Sep. 30, 2012 Guarantor Subsidiaries	Sep. 30, 2013 Guarantor Subsidiaries	Sep. 30, 2012 Guarantor Subsidiaries		Dec. 31, 2012 Guarantor Subsidiaries	Sep. 30, 2013 Non-Guarantor Subsidiaries	Sep. 30, 2012 Non-Guarantor Subsidiaries	Sep. 30, 2013 Non-Guarantor Subsidiaries	Sep. 30, 2012 Non-Guarantor Subsidiaries		Dec. 31, 2012 Non-Guarantor Subsidiaries	Sep. 30, 2013 Consolidating Adjustments	Sep. 30, 2012 Consolidating Adjustments	Sep. 30, 2013 Consolidating Adjustments	Sep. 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	224.6	255.6	224.6	255.6			5.0	5.0	5.0	5.0			217.1	250.0	217.1	250.0			2.5	0.6	2.5	0.6			0	0	0	0
Short-term investments	115.9		115.9			85.0	0		0			0	115.9		115.9			85.0	0		0			0	0		0			0
Receivables:
Trade, less allowance for doubtful receivables	122.1		122.1			123.8	0		0			0	118.8		118.8			121.5	3.3		3.3			2.3	0		0			0
Intercompany (payables) receivables	0		0			0	0		0			0	0.1		0.1			(10.3)	0.2		0.2			0.4	(0.3)		(0.3)			9.9
Other	14.5		14.5			3.4	0		0			0	1.7		1.7			1.3	12.8		12.8			2.1	0		0			0
Inventories	207.9		207.9			186.0	0		0			0	202.6		202.6			178.7	5.8		5.8			7.3	(0.5)		(0.5)			0
Prepaid expenses and other current assets	67.6		67.6			70.1	0.2		0.2			0	66.0		66.0			68.1	1.4		1.4			2.0	0		0			0
Total current assets	752.6		752.6			741.7	5.2		5.2			5.0	722.2		722.2			710.3	26.0		26.0			16.5	(0.8)		(0.8)			9.9
Investments in and advances to subsidiaries	0		0			0	1,399.8		1,399.8			1,284.1	20.8		20.8			7.4	0		0			0	(1,420.6)		(1,420.6)			(1,291.5)
Property, plant, and equipment – net	411.7		411.7			384.3	0		0			0	397.8		397.8			371.8	13.9		13.9			12.5	0		0			0
Long-term intercompany receivables	0		0			0	85.1		85.1			163.7	1.6		1.6			0.4	8.5		8.5			6.4	(95.2)		(95.2)			(170.5)
Net asset in respect of VEBA	385.7		385.7			365.9	0		0			0	385.7		385.7			365.9	0		0			0	0		0			0
Deferred tax assets (liabilities) — net	61.6		61.6			102.0	0		0			0	52.4		52.4			93.4	0		0			(0.8)	9.2		9.2			9.4
Intangible assets – net	34.1		34.1			35.4	0		0			0	34.1		34.1			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	109.1		109.1			86.0	90.4		90.4			64.0	18.5		18.5			19.2	0.2		0.2			3.0	0		0			(0.2)
Total	1,792.0		1,792.0			1,752.5	1,580.5		1,580.5			1,516.8	1,670.3		1,670.3			1,641.0	48.6		48.6			37.6	(1,507.4)		(1,507.4)			(1,442.9)
Current liabilities:
Accounts payable	71.3		71.3			62.5	0		0			0.1	65.8		65.8			56.5	5.5		5.5			5.9	0		0			0
Intercompany payable	0		0			0	0		0			0	10.5		10.5			0.3	0.1		0.1			0.2	(10.6)		(10.6)			(0.5)
Accrued salaries, wages, and related expenses	39.0		39.0			39.3	0		0			0	35.4		35.4			36.7	3.6		3.6			2.6	0		0			0
Other accrued liabilities	40.9		40.9			51.8	10.1		10.1			3.5	29.6		29.6			47.8	1.2		1.2			0.5	0		0			0
Payable to affiliate	0		0			7.9						0						7.9						0						0
Short-term capital lease	0.2		0.2			0.1	0		0			0	0.2		0.2			0.1	0		0			0	0		0			0
Total current liabilities	151.4		151.4			161.6	10.1		10.1			3.6	141.5		141.5			149.3	10.4		10.4			9.2	(10.6)		(10.6)			(0.5)
Net liability in respect of VEBA	4.0		4.0			5.3	0		0			0	4.0		4.0			5.3	0		0			0	0		0			0
Deferred tax liability	1.1		1.1			0	0		0				0		0				1.1		1.1				0		0
Long-term intercompany payable	0		0			0	0		0			0	93.7		93.7			170.0	1.5		1.5			0.5	(95.2)		(95.2)			(170.5)
Long-term liabilities	154.0		154.0			134.5	88.9		88.9			62.1	48.2		48.2			49.6	16.9		16.9			22.8	0		0			0
Long-term debt	386.4		386.4			380.3	386.4		386.4			380.3	0		0			0	0		0			0	0		0			0
Total liabilities	696.9		696.9			681.7	485.4		485.4			446.0	287.4		287.4			374.2	29.9		29.9			32.5	(105.8)		(105.8)			(171.0)
Total stockholders’ equity	1,095.1		1,095.1			1,070.8	1,095.1		1,095.1			1,070.8	1,382.9		1,382.9			1,266.8	18.7		18.7			5.1	(1,401.6)		(1,401.6)			(1,271.9)
Total	1,792.0		1,792.0			1,752.5	1,580.5		1,580.5			1,516.8	1,670.3		1,670.3			1,641.0	48.6		48.6			37.6	(1,507.4)		(1,507.4)			(1,442.9)
CONDENSED CONSOLIDATING STATEMENT OF COMPREHENSIVE INCOME
Net sales	319.9	335.5	986.2	1,046.1			0	0	0	0			315.1	328.6	971.6	1,019.1			29.1	32.0	89.1	96.7			(24.3)	(25.1)	(74.5)	(69.7)
Cost of products sold:
Cost of products sold, excluding depreciation and amortization and other items	259.5	268.9	784.6	851.4			0	0	0	0			255.8	263.7	774.4	831.0			26.8	29.7	80.1	88.6			(23.1)	(24.5)	(69.9)	(68.2)
Unrealized (gains) losses on derivative instruments	(1.5)	(12.3)	3.4	(15.3)			0	0	0	0			(1.5)	(12.3)	3.4	(15.3)			0	0	0	0			0	0	0	0
Depreciation and amortization	6.9	6.7	20.9	19.6			0	0	0	0			6.6	6.4	20.1	18.8			0.3	0.3	0.8	0.8			0	0	0	0
Selling, administrative, research and development, and general	13.4	16.0	45.6	48.3			1.3	0.4	2.8	1.7			11.3	14.0	40.6	45.2			2.0	2.1	6.5	2.8			(1.2)	(0.5)	(4.3)	(1.4)
Other operating charges, net	0	0	0	0.1						0						0.1						0						0
Total costs and expenses	278.3	279.3	854.5	904.1			1.3	0.4	2.8	1.7			272.2	271.8	838.5	879.8			29.1	32.1	87.4	92.2			(24.3)	(25.0)	(74.2)	(69.6)
Operating (loss) income	41.6	56.2	131.7	142.0			(1.3)	(0.4)	(2.8)	(1.7)			42.9	56.8	133.1	139.3			0	(0.1)	1.7	4.5			0	(0.1)	(0.3)	(0.1)
Other (expense) income:
Interest (expense) income	(8.8)	(9.2)	(27.1)	(19.8)			(9.2)	(9.0)	(27.3)	(19.2)			0.3	(0.2)	0	(0.6)			0	0	0	0			0.1	0	0.2	0
Other income, net	2.9	0.4	3.1	2.2			2.2	0	1.7	1.2			0.5	0.3	1.4	0.8			0.4	0.1	0.3	0.2			(0.2)	0	(0.3)	0
(Loss) income before income taxes	35.7	47.4	107.7	124.4			(8.3)	(9.4)	(28.4)	(19.7)			43.7	56.9	134.5	139.5			0.4	0	2.0	4.7			(0.1)	(0.1)	(0.4)	(0.1)
Income tax (provision) benefit	(10.3)	(18.2)	(30.2)	(47.7)			0	0	0	0			(18.0)	(21.6)	(52.1)	(53.1)			4.4	(0.6)	10.9	(2.0)			3.3	4.0	11.0	7.4
Earnings in equity of subsidiaries	0	0	0	0			33.7	38.6	105.9	96.4			4.8	(0.7)	12.5	2.6			0	0	0	0			(38.5)	(37.9)	(118.4)	(99.0)
Net income	25.4	29.2	77.5	76.7			25.4	29.2	77.5	76.7			30.5	34.6	94.9	89.0			4.8	(0.6)	12.9	2.7			(35.3)	(34.0)	(107.8)	(91.7)
Comprehensive income	26.0	30.1	80.6	80.2			26.0	30.1	80.6	80.2			31.4	36.0	97.5	92.9			4.5	(1.1)	13.4	2.3			(35.9)	(34.9)	(110.9)	(95.2)
Cash flows from operating activities:
Net cash (used in) provided by operating activities			90.6	106.7					(15.6)	(4.0)					102.8	106.0					3.4	4.7					0	0
Cash flows from investing activities:
Capital expenditures	(21.0)	(8.8)	(47.0)	(25.7)					0	0					(44.8)	(24.6)					(2.2)	(1.1)					0	0
Purchase of available for sale securities			(201.8)	(80.0)					0	0					(201.8)	(80.0)					0	0					0	0
Proceeds from disposition of available for sale securities			170.7	0					0						170.7						0						0
Change in restricted cash			0.7	6.8					0	6.9					0.7	0.3					0	(0.4)					0	0
Net cash provided by (used in) investing activities			(77.4)	(98.9)					0	6.9					(75.2)	(104.3)					(2.2)	(1.5)					0	0
Cash flows from financing activities:
Repayment of capital lease			0	(0.1)						0						(0.1)						0						0
Proceeds from issuance of senior notes			0	225.0						225.0						0						0						0
Cash paid for financing costs			0	(6.6)						(6.6)						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			1.0	1.3					0	0					1.0	1.3					0	0					0	0
Cancellation of shares to cover employees’ tax withholdings upon vesting of non-vested shares			(2.4)	(2.2)					(2.4)	(2.2)					0	0					0	0					0	0
Cash dividend paid to stockholders			(17.3)	(14.7)					(17.3)	(14.7)					0	0					0	0					0	0
Cash dividend returned to the Company			0.6	0					0.6						0						0						0
Repurchase of common stock			(43.9)	0					(43.9)						0						0						0
Intercompany loan			0	0	[1]				78.6	(204.4)	[1]				(77.5)	208.8	[1]				(1.1)	(4.4)	[1]				0	0	[1]
Net cash provided by (used in) financing activities			(62.0)	198.0					15.6	(2.9)					(76.5)	205.3					(1.1)	(4.4)					0	0
Net (decrease) increase in cash and cash equivalents during the period			(48.8)	205.8					0	0					(48.9)	207.0					0.1	(1.2)					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	$ 224.6	$ 255.6	$ 224.6	$ 255.6			$ 5.0	$ 5.0	$ 5.0	$ 5.0			$ 217.1	$ 250.0	$ 217.1	$ 250.0			$ 2.5	$ 0.6	$ 2.5	$ 0.6			$ 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 the nine months ended September 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.