Tax Effects of Temporary Differences and Carryforwards that Give Rise to Deferred Income Tax Assets and Liabilities (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Deferred tax assets:
Inventory reserves	$ 18.3	$ 17.3
Warranty reserves	9.3	6.9
Accrued liabilities	15.5	17.5
Net operating loss carryforward	19.6	14.8
Research and development credit carry forward	38.2	32.6
Alternative minimum tax credit carryforward	5.0	5.3
Other	4.7	5.1
Deferred Tax Assets, Gross, Total	110.6	99.5
Deferred tax liabilities:
Book to tax revenue differences	(37.5)	(34.5)
Intangible assets	(92.8)	(76.1)
Depreciation	(23.2)	(14.3)
Software development costs	(1.3)	(1.9)
Deferred Tax Liabilities	(154.8)	(126.8)
Net deferred tax liability before valuation allowance	(44.2)	(27.3)
Valuation allowance	(20.1)	(14.4)
Net deferred tax liability	$ (64.3)	$ (41.7)