Bank Revolving Credit Facility (Details Textual) (USD $)			9 Months Ended			9 Months Ended
	Oct. 31, 2013	Jan. 31, 2013	Oct. 31, 2013 Revolving credit facility [Member]	Jul. 03, 2013 Revolving credit facility [Member]	Feb. 28, 2013 Revolving credit facility [Member]	Oct. 31, 2013 Common stock Class A [Member] Revolving credit facility [Member]	Oct. 31, 2013 Common Class A or B [Member] Revolving credit facility [Member]	Oct. 31, 2013 Senior Notes due 2017 [Member]	Jan. 31, 2013 Senior Notes due 2017 [Member]	Oct. 31, 2013 Senior Notes due 2034 [Member]	Jan. 31, 2013 Senior Notes due 2034 [Member]
Line of Credit Facility [Line Items]
Total available borrowings	$ 500,000,000	$ 450,000,000		$ 500,000,000	$ 465,000,000
Total available borrowing capacity under accordion provision					500,000,000
Credit Facility maturity terms			February 21, 2016 and provides for one, 12-month extension option
Number of Credit Facility extension options			1
Term of Credit Facility extension option			12 months
Credit Facility interest rate			LIBOR plus 3.50%
Variable rate basis of debt instrument			LIBOR
Variable rate basis spread of debt instrument			3.50%
Amount of available borrowings that can be used for letters of credit and/or surety bonds					100,000,000
Maximum Class A common stock repurchase amount						100,000,000
Maximum dividend restriction in any four fiscal quarter period							$ 24,000,000
Interest rate								6.50%	6.50%	7.375%	7.375%