Financing Liability for Construction in Progress - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	1 Months Ended	12 Months Ended
	Jan. 31, 2010	Dec. 31, 2010	Dec. 31, 2009
Structural leasehold improvement costs incurred during construction	$ 18.9
Construction costs reimbursed by the landlord	18.8
Fair value of the building capitalized			6.9
Increased liability due to additional structural leasehold improvements		18.9
Increased liability due to land lease expense		0.2
Increased liability due to capitalized interest expense		$ 0.2