Segment Reporting, Geographic and Customer Information - Additional Information (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2016 USD ($) Segment Customer	Dec. 31, 2015 USD ($) Customer	Dec. 31, 2014 USD ($) Customer
Segment Reporting Information [Line Items]
Number of operating segments | Segment	5
Number of reportable segments | Segment	4
Gain (loss) on foreign currency exchange rate of west corporation or any of its subsidiaries | $	$ (0.9)	$ (2.5)	$ 2.0
Customer Concentration Risk [Member]
Segment Reporting Information [Line Items]
Number of customers | Customer	3
Revenues [Member] | Customer Concentration Risk [Member]
Segment Reporting Information [Line Items]
Percentages of consolidated revenue	43.00%	44.00%	47.00%
Number of customers | Customer	100	100	100
Revenues [Member] | Customer Concentration Risk [Member] | Maximum [Member]
Segment Reporting Information [Line Items]
Percentages of consolidated revenue	6.00%	6.00%	6.00%
Revenues [Member] | Geographic Concentration Risk [Member] | United Kingdom [Member]
Segment Reporting Information [Line Items]
Percentages of consolidated revenue	12.00%	13.00%	13.00%
Revenues [Member] | Geographic Concentration Risk [Member] | Minimum [Member] | United Kingdom [Member]
Segment Reporting Information [Line Items]
Percentages of consolidated revenue	10.00%	10.00%	10.00%