Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended			6 Months Ended
	Jul. 31, 2018	Jan. 31, 2018	Jul. 31, 2017	Jul. 31, 2018	Jul. 31, 2017
Schedule of tax impact from settlement [Line Items]
US Tax Act Impact		$ 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	6.80%		36.70%	11.70%	34.60%
Provision for income taxes	$ 5,545		$ 27,516	$ 14,503	$ 41,347
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount				(2,600)
TS
Schedule of tax impact from settlement [Line Items]
Deferred Other Tax Expense (Benefit)	$ (12,800)			$ (12,800)