Reconciliation of Assets Measured at Fair Value on Recurring Basis (Detail) (USD $) In Millions, unless otherwise specified				6 Months Ended		12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2011 Real Estate Funds		Dec. 31, 2012 Real Estate Funds
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at beginning of period	$ 102.7	$ 102.5	$ 70.9	$ 7.7	[1]	$ 7.7	[1]
Actual return on plan assets related to assets still held				0.2	[1]
Foreign currency translation				(0.2)	[1]	0.5
Balance at end of year	$ 102.7	$ 102.5	$ 70.9	$ 7.7	[1]	$ 8.2

[1] For the period July 1, 2011 (date of acquisition) to December 31, 2011.