Bank Revolving Credit Facility Bank Revolving Credit Facility (Details 1) (USD $)						0 Months Ended		12 Months Ended	0 Months Ended
	Jan. 31, 2013		Jan. 31, 2012		Jan. 31, 2013 Revolving Credit Facility [Member]	Feb. 21, 2013 Revolving Credit Facility [Member] Subsequent Event [Member]	Feb. 21, 2013 Common Class A or B [Member] Revolving Credit Facility [Member] Subsequent Event [Member]	Jan. 31, 2013 LIBOR [Member] Revolving Credit Facility [Member]	Feb. 21, 2013 LIBOR [Member] Revolving Credit Facility [Member] Subsequent Event [Member]
Subsequent Event [Line Items]
Credit facility, maturity date extension period						1 year
Reduction in basis spread on LIBOR									0.25%
Debt instrument variable rate basis spread								3.75%	3.50%
Debt instrument floor rate								1.00%
Maximum borrowings	$ 450,000,000	[1]	$ 450,000,000	[1]	$ 450,000,000	$ 465,000,000
Maximum borrowing capacity with accordion provision						500,000,000
Amendment option to repurchase common stock						100,000,000
Maximum dividend restriction in any four fiscal quarter period							$ 24,000,000

[1] The maximum borrowings under the Credit Facility was increased to $465,000,000 on February 21, 2013, upon entering into the fourth amendment to the Credit Facility, as discussed below.