Property and Equipment - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	1 Months Ended	12 Months Ended
	Nov. 30, 2010 acre	Jan. 31, 2013	Jan. 31, 2012	Jan. 31, 2011
Property, Plant and Equipment [Line Items]
Depreciation and amortization expense		$ 101.1	$ 69.8	$ 41.4
Fixed assets acquired under capital lease agreements		136.9	105.1
Accumulated amortization relating to computers, equipment and software under capital leases		57.8	31.7
Acres of undeveloped real estate purchased	14
Perpetual parking rights	23.3
Pre-construction costs capitalized		5.7
Total carrying value of the land, building improvements and perpetual parking rights		$ 321.1