Industry Segment and Geographic Information Segment Reporting (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Total revenues	$ 309,687	$ 302,534	$ 297,584	$ 279,541	$ 273,803	$ 261,531	$ 259,875	$ 253,573	$ 1,189,346	$ 1,048,782	$ 1,002,286
Cost of revenues									511,084	426,995	404,954
Gross Profit									$ 678,262	$ 621,787	$ 597,332
Segment gross margin %									57.00%	59.30%	59.60%
Cost, depreciation and amortization									$ 38,167	$ 27,754	$ 27,308
Sales and marketing									363,111	311,433	313,251
Engineering and development									69,460	52,139	29,630
General and administrative									152,672	135,324	122,537
Depreciation and amortization									86,256	70,980	72,523
(Loss) income from operations	$ 3,975	$ 5,547	$ (167)	$ (2,592)	$ 6,021	$ 14,847	$ 13,375	$ 17,668	6,763	51,911	59,391
Interest expense									32,821	15,068	14,868
Other income (expense), net									(50)	(318)	1,270
Income before income taxes									(26,108)	36,525	45,793
Business Service
Segment Reporting Information [Line Items]
Total revenues									803,880	608,144	498,922
Cost of revenues									427,634	328,551	268,793
Gross Profit									$ 376,246	$ 279,593	$ 230,129
Segment gross margin %									46.80%	46.00%	46.10%
Cost, depreciation and amortization									$ 33,484	$ 22,554	$ 20,100
Consumer Service
Segment Reporting Information [Line Items]
Total revenues									385,466	440,638	503,364
Cost of revenues									83,450	98,444	136,161
Gross Profit									$ 302,016	$ 342,194	$ 367,203
Segment gross margin %									78.40%	77.70%	72.90%
Cost, depreciation and amortization									$ 4,683	$ 5,200	$ 7,208
Service
Segment Reporting Information [Line Items]
Total revenues									1,059,976	921,096	871,458
Cost of revenues									370,722	286,535	264,508
Gross Profit									$ 689,254	$ 634,561	$ 606,950
Segment gross margin %									65.00%	68.90%	69.60%
Service | Business Service
Segment Reporting Information [Line Items]
Total revenues									$ 719,514	$ 526,707	$ 417,118
Cost of revenues									336,045	239,096	184,054
Gross Profit									$ 383,469	$ 287,611	$ 233,064
Segment gross margin %									53.30%	54.60%	55.90%
Service | Consumer Service
Segment Reporting Information [Line Items]
Total revenues									$ 340,462	$ 394,389	$ 454,340
Cost of revenues									34,677	47,439	80,454
Gross Profit									$ 305,785	$ 346,950	$ 373,886
Segment gross margin %									89.80%	88.00%	82.30%
Product
Segment Reporting Information [Line Items]
Total revenues									$ 46,496	$ 50,627	$ 55,496
Cost of revenues									57,488	63,370	65,114
Gross Profit									(10,992)	(12,743)	(9,618)
Product | Business Service
Segment Reporting Information [Line Items]
Total revenues									46,232	50,068	54,971
Cost of revenues									53,455	58,081	57,906
Gross Profit									(7,223)	(8,013)	(2,935)
Product | Consumer Service
Segment Reporting Information [Line Items]
Total revenues									264	559	525
Cost of revenues									4,033	5,289	7,208
Gross Profit									(3,769)	(4,730)	(6,683)
Service and Product
Segment Reporting Information [Line Items]
Total revenues									1,106,472	971,723	926,954
Cost of revenues									428,210	349,905	329,622
Gross Profit									$ 678,262	$ 621,818	$ 597,332
Segment gross margin %									61.30%	64.00%	64.40%
Service and Product | Business Service
Segment Reporting Information [Line Items]
Total revenues									$ 765,746	$ 576,775	$ 472,089
Cost of revenues									389,500	297,177	241,960
Gross Profit									$ 376,246	$ 279,598	$ 230,129
Segment gross margin %									49.10%	48.50%	48.70%
Service and Product | Consumer Service
Segment Reporting Information [Line Items]
Total revenues									$ 340,726	$ 394,948	$ 454,865
Cost of revenues									38,710	52,728	87,662
Gross Profit									$ 302,016	$ 342,220	$ 367,203
Segment gross margin %									88.60%	86.60%	80.70%
USF
Segment Reporting Information [Line Items]
Total revenues									$ 82,874	$ 77,059	$ 75,332
Cost of revenues									82,874	77,090	75,332
Gross Profit									0	(31)	0
USF | Business Service
Segment Reporting Information [Line Items]
Total revenues									38,134	31,369	26,833
Cost of revenues									38,134	31,374	26,833
Gross Profit									0	(5)	0
USF | Consumer Service
Segment Reporting Information [Line Items]
Total revenues									44,740	45,690	48,499
Cost of revenues									44,740	45,716	48,499
Gross Profit									$ 0	$ (26)	$ 0