Shareholders' Equity (Details) - USD ($) $ / shares in Units, $ in Thousands	6 Months Ended
	Jul. 31, 2015	Jan. 31, 2015
Equity, Class of Treasury Stock
Treasury Stock, Number of Shares Held	23,579,636	21,866,069
Treasury Stock Held, Average Cost Per Share	$ 44.16	$ 42.95
Stock Repurchased During Period, Shares	1,893,838
Stock Repurchased During Period, Cost Per Share	$ 58.13
Stock Issued During Period, Shares, Treasury Stock Reissued	(180,271)
December 2014 Program
Equity, Class of Treasury Stock
Stock Repurchase Program, Authorized Amount		$ 100,000
June 2015 Program [Member]
Equity, Class of Treasury Stock
Stock Repurchase Program, Authorized Amount	$ 100,000