Stock-Based Compensation - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		0 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013 Liability Classified Awards [Member]	Jun. 30, 2012 Liability Classified Awards [Member]	Jun. 30, 2013 Liability Classified Awards [Member]	Jun. 30, 2012 Liability Classified Awards [Member]	Jun. 30, 2013 Equity Classified Awards [Member]	Jun. 30, 2012 Equity Classified Awards [Member]	Jun. 30, 2013 Equity Classified Awards [Member]	Jun. 30, 2012 Equity Classified Awards [Member]	Jun. 28, 2013 Restricted Stock Units (RSUs) [Member]	Jun. 28, 2013 Annual [Member] Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expense related to stock-based awards of subsidiaries	$ 2.6	$ 16.2	$ 3.9	$ 16.2	$ 1.8	$ 15.5	$ 2.3	$ 15.5	$ 0.8	$ 0.7	$ 1.6	$ 0.7
Restricted stock units granted													1.6
Fair value of restricted stock units granted													$ 21.3
Vesting percentage														25.00%