Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Apr. 30, 2017	Apr. 30, 2016
Earnings Per Share [Abstract]
Net income	$ 30,654	$ 33,373
Weighted average common shares - basic	37,251,000	35,127,000
Equity based awards	217,000	243,000
Weighted average common shares - diluted	37,468,000	35,370,000
Basic EPS	$ 0.82	$ 0.95
Diluted EPS	$ 0.82	$ 0.94
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	0	200,383