Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended
	Apr. 30, 2018	Jan. 31, 2018	Apr. 30, 2017
Income Taxes [Abstract]
US Tax Act Impact	$ 95,400	$ 95,400
US Tax Act Impact - Transition Tax		101,100
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Amount		$ (5,700)
Effective Income Tax Rate Reconciliation, Percent	21.00%		31.10%
Provision for income taxes	$ 8,958		$ 13,831
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount	$ (2,600)