Goodwill and Intangible Assets - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Goodwill And Intangible Assets Disclosure [Abstract]
Amortization expense on identifiable intangible assets	$ 13.3	$ 7.5	$ 33.0	$ 22.6
Expected amortization expenses in year one	50		50
Expected amortization expenses in year two	53		53
Expected amortization expenses in year three	53		53
Expected amortization expenses in year four	53		53
Expected amortization expenses in year five	53		53
Goodwill increase during period			682.6
Preliminary estimate of goodwill associated with acquisitions in 2013 and 2014			$ 717.1