Fair Value Measurements (Details) - USD ($) $ in Thousands	Jan. 31, 2018	Jan. 31, 2017
Senior Notes
Liabilities, Fair Value Disclosure
Debt, fair value disclosures	$ 1,020,000	$ 1,354,000
Term Loan [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Loans Payable, Noncurrent	500,000
Level 1 | Fair Value, Measurements, Recurring
Assets, Fair Value Disclosure
Cash and Cash Equivalents, Fair Value Disclosure	0	1,000,010
Level 2 | Fair Value, Measurements, Recurring
Assets, Fair Value Disclosure
Foreign currency forward contracts	5,025	2,264
Liabilities, Fair Value Disclosure
Foreign currency forward contracts	$ 11,675	$ 9,711