Method of Overhead Allocation (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Jan. 31, 2014	Oct. 31, 2013	Jul. 31, 2013	Apr. 30, 2013	Jan. 31, 2013	Oct. 31, 2012	Jul. 31, 2012	Apr. 30, 2012	Jan. 31, 2014	Jan. 31, 2013	Jan. 31, 2012
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	$ 472,756	$ 668,702	$ 304,158	$ 272,615	$ 375,278	$ 543,513	$ 251,479	$ 229,449	$ 1,718,231	$ 1,399,719	$ 1,231,201
Long-Lived Assets	244,707				201,188				244,707	201,188	81,325
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues									1,528,473	1,333,885	1,185,800
Long-Lived Assets	106,638				81,606				106,638	81,606	80,817
Non-United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues									189,758	65,834	45,401
Long-Lived Assets	$ 138,069				$ 119,582				$ 138,069	$ 119,582	$ 508