Stockholders' Equity (Restricted Stock Activity) (Details) - Restricted Stock - $ / shares	12 Months Ended
	Jan. 31, 2017	Jan. 31, 2016	Jan. 31, 2015
Shares
Outstanding, beginning of period	827,200	559,200
Shares granted	264,200	497,800
Shares vested	(246,500)	(171,400)
Shares forfeited	(76,600)	(58,400)
Outstanding, end of period	768,300	827,200	559,200
Weighted Average Grant Date Fair Value
Outstanding, beginning of period	$ 35.96	$ 38.09
Shares granted	41.64	33.42
Shares vested	35.72	34.65
Shares forfeited	35.96	38.56
Outstanding, end of period	$ 37.99	$ 35.96	$ 38.09
Weighted Average Remaining Vesting Period
Weighted Average Remaining Vesting Period	2 years 5 months 23 days	3 years 1 month 13 days	2 years 11 months 19 days