Derivatives and Hedging Activities - Summary of Open Foreign Currency Contracts (Details) £ in Thousands, CAD in Thousands, $ in Thousands	Apr. 30, 2017 CAD	Apr. 30, 2017 GBP (£)	Apr. 30, 2017 USD ($)
Derivative [Line Items]
Number of Instruments	18	18	18
Sell USD/Buy CAD Forward Contract [Member]
Derivative [Line Items]
Number of Instruments	9	9	9
Sell USD/Buy GBP Forward Contract [Member]
Derivative [Line Items]
Number of Instruments	9	9	9
Short [Member] | Sell USD/Buy CAD Forward Contract [Member]
Derivative [Line Items]
Notional Value | CAD	CAD 20,250
Short [Member] | Sell USD/Buy GBP Forward Contract [Member]
Derivative [Line Items]
Notional Value | £		£ 6,750
Long [Member] | Sell USD/Buy CAD Forward Contract [Member]
Derivative [Line Items]
Notional Value			$ 14,904
Long [Member] | Sell USD/Buy GBP Forward Contract [Member]
Derivative [Line Items]
Notional Value			$ 8,271