Fan Pier Leases (Details) (USD $) In Millions, unless otherwise specified	1 Months Ended	3 Months Ended
	May 31, 2011 buildings area leases	Mar. 31, 2012 Y	Dec. 31, 2011
Fan Pier Leases
Number of leases	2
Area of leased property (in square feet)	1,100,000
Number of buildings under lease agreement	2
Initial term of lease agreement (in years)		15
Optional term of lease agreement (in years)		10
Project construction costs incurred by landlord		$ 92.9	$ 54.7
Rent expense related to land operating lease		$ 1.6