Quarterly Results of Operations-Unaudited - Quarterly Results of Operations (Parenthetical) (Detail) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended			12 Months Ended
	Jan. 31, 2017	Jan. 31, 2018	Jan. 31, 2017	Jul. 31, 2016	Jan. 31, 2018	Jan. 31, 2017	Jan. 31, 2016
Schedule Of Quarterly Financial Information [Line Items]
Income tax (benefit) provision		$ (14,700)		$ 14,600	$ (12,272)	$ 14,631	$ (1,029)
Undistributed earnings of foreign subsidiaries				$ 58,600
Loss on impairment of long-lived assets	$ 500		$ 23,500			$ 23,772	$ 21,464
Impairment charge to write down investment in affiliate			500
T-Mobile [Member] | Layer3 TV, Inc. [Member]
Schedule Of Quarterly Financial Information [Line Items]
Gain on sale of investment		$ 2,600
Operating Income (Loss) [Member]
Schedule Of Quarterly Financial Information [Line Items]
Loss on impairment of long-lived assets			23,700
New Hampshire [Member]
Schedule Of Quarterly Financial Information [Line Items]
Loss on impairment of long-lived assets			$ 200