Segment Reporting, Geographic and Customer Information - Revenue and Long-Lived Assets for Each Reportable Segment by Geographical Region (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Revenue:
REVENUE	$ 574,393	$ 582,397	$ 1,146,935	$ 1,153,176
Long-Lived Assets:
Long-Lived Assets	2,748,014		2,748,014		$ 2,746,543
Operating Segments [Member] | Unified Communications Services [Member]
Revenue:
REVENUE	348,546	370,158	699,621	732,871
Operating Segments [Member] | Safety Services [Member]
Revenue:
REVENUE	80,419	74,423	156,674	145,587
Operating Segments [Member] | Interactive Services [Member]
Revenue:
REVENUE	79,179	73,232	156,672	144,961
Operating Segments [Member] | Specialized Agent Services [Member]
Revenue:
REVENUE	69,354	67,495	141,102	135,873
Eliminations [Member]
Revenue:
REVENUE	(3,105)	(2,911)	(7,134)	(6,116)
Americas - United States [Member]
Revenue:
REVENUE	465,945	459,330	930,816	911,760
Long-Lived Assets:
Long-Lived Assets	2,532,710		2,532,710		2,546,361
Americas - United States [Member] | Operating Segments [Member] | Unified Communications Services [Member]
Revenue:
REVENUE	244,378	250,742	492,049	498,424
Americas - United States [Member] | Operating Segments [Member] | Safety Services [Member]
Revenue:
REVENUE	78,535	73,384	153,012	143,041
Americas - United States [Member] | Operating Segments [Member] | Interactive Services [Member]
Revenue:
REVENUE	76,783	70,620	151,787	140,538
Americas - United States [Member] | Operating Segments [Member] | Specialized Agent Services [Member]
Revenue:
REVENUE	69,354	67,495	141,102	135,873
Americas - United States [Member] | Eliminations [Member]
Revenue:
REVENUE	(3,105)	(2,911)	(7,134)	(6,116)
Europe, Middle East & Africa [Member]
Revenue:
REVENUE	68,503	81,430	137,193	160,825
Long-Lived Assets:
Long-Lived Assets	182,977		182,977		172,439
Europe, Middle East & Africa [Member] | Operating Segments [Member] | Unified Communications Services [Member]
Revenue:
REVENUE	67,977	80,774	136,152	159,424
Europe, Middle East & Africa [Member] | Operating Segments [Member] | Safety Services [Member]
Revenue:
REVENUE	29	18	64	41
Europe, Middle East & Africa [Member] | Operating Segments [Member] | Interactive Services [Member]
Revenue:
REVENUE	497	638	977	1,360
Europe, Middle East & Africa [Member] | Operating Segments [Member] | Specialized Agent Services [Member]
Revenue:
REVENUE	0	0	0	0
Europe, Middle East & Africa [Member] | Eliminations [Member]
Revenue:
REVENUE	0	0	0	0
Asia Pacific [Member]
Revenue:
REVENUE	35,145	36,473	68,635	71,129
Long-Lived Assets:
Long-Lived Assets	23,435		23,435		18,495
Asia Pacific [Member] | Operating Segments [Member] | Unified Communications Services [Member]
Revenue:
REVENUE	34,036	35,927	66,913	70,010
Asia Pacific [Member] | Operating Segments [Member] | Safety Services [Member]
Revenue:
REVENUE	550	0	647	75
Asia Pacific [Member] | Operating Segments [Member] | Interactive Services [Member]
Revenue:
REVENUE	559	546	1,075	1,044
Asia Pacific [Member] | Operating Segments [Member] | Specialized Agent Services [Member]
Revenue:
REVENUE	0	0	0	0
Asia Pacific [Member] | Eliminations [Member]
Revenue:
REVENUE	0	0	0	0
Americas - Other [Member]
Revenue:
REVENUE	4,800	5,164	10,291	9,462
Long-Lived Assets:
Long-Lived Assets	8,892		8,892		$ 9,248
Americas - Other [Member] | Operating Segments [Member] | Unified Communications Services [Member]
Revenue:
REVENUE	2,155	2,715	4,507	5,013
Americas - Other [Member] | Operating Segments [Member] | Safety Services [Member]
Revenue:
REVENUE	1,305	1,021	2,951	2,430
Americas - Other [Member] | Operating Segments [Member] | Interactive Services [Member]
Revenue:
REVENUE	1,340	1,428	2,833	2,019
Americas - Other [Member] | Operating Segments [Member] | Specialized Agent Services [Member]
Revenue:
REVENUE	0	0	0	0
Americas - Other [Member] | Eliminations [Member]
Revenue:
REVENUE	$ 0	$ 0	$ 0	$ 0