Leases - Lease assets and liabilities (Details) - USD ($) $ in Thousands	Jul. 31, 2021	Jan. 31, 2021	Jul. 31, 2020
Assets and Liabilities, Lessee [Abstract]
Operating lease assets	$ 172,916	$ 186,070	$ 168,071
Classification of operating lease assets	Operating lease assets
Total lease assets	$ 172,916	186,070	168,071
Current operating lease liabilities	$ 43,119	43,560	91,700
Classification current operating lease liabilities	Current operating lease liabilities
Noncurrent operating lease liabilities	$ 147,119	161,668	140,283
Classification of noncurrent operating liabilities	Noncurrent operating lease liabilities
Total lease liabilities	$ 190,238	$ 205,228	$ 231,983