Commitments and Contingencies (Detail) $ in Millions |
1 Months Ended | 3 Months Ended | |
|---|---|---|---|
|
Jan. 31, 2014
USD ($)
a
|
Apr. 30, 2017
USD ($)
|
Apr. 30, 2016
USD ($)
|
|
| Commitments and Contingencies Disclosure [Abstract] | |||
| Rent expense | $ 19.0 | $ 17.0 | |
| Lease term period | 95 years | ||
| Parcel of vacant land (in acres) | a | 6.9 | ||
| Lease rent, prepaid | $ 2.0 | ||
| Annual rent payments plus increases based on increases in consumer price index | $ 0.2 | ||