Segment Reporting, Geographic and Customer Information - Additional Information (Detail) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016 USD ($) Customer	Sep. 30, 2015 USD ($)	Sep. 30, 2016 USD ($) Segment Customer	Sep. 30, 2015 USD ($)
Foreign Currency Translation [Line Items]
Number of operating segments			5
Number of reportable segments			4
Foreign currency exchange rate of west corporation or any of its subsidiaries | $	$ 1.0	$ 1.3	$ 2.0	$ 1.6
Revenues [Member] | Geographic Concentration Risk [Member] | Non-U.S Countries [Member]
Foreign Currency Translation [Line Items]
Percentages of consolidated revenue	19.00%	20.00%	20.00%	21.00%
Revenues [Member] | Geographic Concentration Risk [Member] | United Kingdom [Member]
Foreign Currency Translation [Line Items]
Percentages of consolidated revenue	11.00%	12.00%	12.00%	12.00%
Revenues [Member] | Geographic Concentration Risk [Member] | United Kingdom [Member] | Minimum [Member]
Foreign Currency Translation [Line Items]
Percentages of consolidated revenue	10.00%	10.00%	10.00%	10.00%
Revenues [Member] | Customer Concentration Risk [Member]
Foreign Currency Translation [Line Items]
Percentages of consolidated revenue	45.00%	45.00%	43.00%	45.00%
Number of customers | Customer	100		100