Stockholders' Equity Stock Repurchase Program (Details) (USD $)	3 Months Ended	6 Months Ended		1 Months Ended	6 Months Ended
	Jul. 31, 2014	Jul. 31, 2014	Jul. 31, 2013	Mar. 31, 2014 2014 Program [Member]	Jul. 31, 2014 2014 Program [Member]
Stock Repurchase [Table] [Line Items]
Cost of repurchases	$ 9,256,000	$ 16,402,000	$ 0
Shares repurchased and retired	102,000	184,000
Average cost per share	$ 90.98	$ 89.18
Stock Repurchase Program, Authorized Amount				300,000,000
Stock Repurchase Program, Remaining Authorized Repurchase Amount					$ 283,598,000