Commitments and Contingencies (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2012
400 WCC
Operating Leases
Purchase option price for buildings (in dollars)	$ 44.3
Contingent liability on sale of leased property to third party (in dollars)	35.3
200 WCC
Operating Leases
Purchase option price for buildings (in dollars)	50.1
Contingent liability on sale of leased property to third party (in dollars)	$ 40.0