Goodwill and Intangible Assets - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Goodwill and Intangible Assets Disclosure [Line Items]
Amortization expense on identifiable intangible assets	$ 7.4	$ 6.3	$ 21.2	$ 19.1
Expected amortization expenses in year one	30		30
Expected amortization expenses in year two	30		30
Expected amortization expenses in year three	30		30
Expected amortization expenses in year four	30		30
Expected amortization expenses in year five	30		30
Goodwill increase during period			481.7
UFC and Interturbine acquisitions
Goodwill and Intangible Assets Disclosure [Line Items]
Goodwill increase during period			$ 470.3