Restructuring Costs - Schedule of Carrying Amount of Accrual for Restructuring Plans (Detail) - USD ($) $ in Thousands	6 Months Ended
	Jul. 31, 2016	Jul. 31, 2015
Restructuring Cost And Reserve [Line Items]
Balance at January 31, 2016	$ 1,213
Total restructuring costs	1,460	$ 3,245
Cash expenditures	(1,452)
Adjustment to liability	35
Balance at July 31, 2016	1,256
Water Resources Business Performance Initiative [Member]
Restructuring Cost And Reserve [Line Items]
Total restructuring costs	603
FY2016 Restructuring Plan [Member]
Restructuring Cost And Reserve [Line Items]
Total restructuring costs	857
Severance and other personnel-related costs [Member]
Restructuring Cost And Reserve [Line Items]
Balance at January 31, 2016	1,157
Total restructuring costs	397
Cash expenditures	(738)
Adjustment to liability	25
Balance at July 31, 2016	841
Severance and other personnel-related costs [Member] | Water Resources Business Performance Initiative [Member]
Restructuring Cost And Reserve [Line Items]
Total restructuring costs	187
Severance and other personnel-related costs [Member] | FY2016 Restructuring Plan [Member]
Restructuring Cost And Reserve [Line Items]
Total restructuring costs	210
Other Restructuring [Member]
Restructuring Cost And Reserve [Line Items]
Balance at January 31, 2016	56
Total restructuring costs	1,063
Cash expenditures	(714)
Adjustment to liability	10
Balance at July 31, 2016	415
Other Restructuring [Member] | Water Resources Business Performance Initiative [Member]
Restructuring Cost And Reserve [Line Items]
Total restructuring costs	416
Other Restructuring [Member] | FY2016 Restructuring Plan [Member]
Restructuring Cost And Reserve [Line Items]
Total restructuring costs	$ 647