Revenue Recognition (Details) - USD ($) $ in Thousands	Apr. 30, 2018	Jan. 31, 2018		Apr. 30, 2017
Assets
Accounts receivable, net of allowance for doubtful accounts	$ 429,146	$ 294,430	[1]	$ 256,212	[1]
Inventories	463,463	553,323		445,969
Prepaid expenses and other current assets	102,072	51,014		55,474
Deferred income tax assets, net	27,982	11,439		15,901
Liabilities
Accrued expenses	86,058	95,055		75,197
Customer refund liabilities	214,693
Equity
Retained earnings	630,633	$ 674,542		$ 602,027
Without Adoption of ASC 606
Assets
Accounts receivable, net of allowance for doubtful accounts	282,902
Inventories	502,819
Prepaid expenses and other current assets	62,859
Deferred income tax assets, net	11,438
Liabilities
Accrued expenses	82,648
Customer refund liabilities	0
Equity
Retained earnings	686,091
Impact of Adoption of ASC 606
Assets
Accounts receivable, net of allowance for doubtful accounts	146,244
Inventories	(39,356)
Prepaid expenses and other current assets	39,213
Deferred income tax assets, net	16,544
Liabilities
Accrued expenses	3,410
Customer refund liabilities	214,693
Equity
Retained earnings	$ (55,458)

[1] Also, net of accrued returns and sales discounts