Effect of Revision on Previously Reported Comprehensive Income (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2012	Mar. 31, 2012	Jun. 30, 2011	Mar. 31, 2011	Jun. 30, 2012	Jun. 30, 2011
Guarantor Subsidiaries
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items]
Impact of revisions on comprehensive income	$ 0.7	$ 1.1	$ 2.4	$ 8.3	$ 1.8	$ 10.7
Non-Guarantor Subsidiaries
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items]
Impact of revisions on comprehensive income	(50.0)	27.4	21.2	39.9	(22.6)	61.1
Consolidation, Eliminations
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items]
Impact of revisions on comprehensive income	$ 49.3	$ (28.5)	$ (23.6)	$ (48.2)	$ 20.8	$ (71.8)