Goodwill and Intangible Assets - Company's Purchased Intangible Assets (Detail) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2021	Dec. 31, 2020
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible assets subject to amortization, Gross Intangibles	$ 210,298	$ 209,855
Intangible assets subject to amortization, Accumulated Amortization	(145,280)	(139,012)
Intangible assets subject to amortization, Net Intangibles	$ 65,018	$ 70,843
Intangible assets subject to amortization, Weighted Average Amortization Period (years)	9 years	9 years
Gross Intangibles, Total	$ 373,171	$ 372,987
Net Intangibles, Total	227,891	233,975
Customer Relationships [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible assets subject to amortization, Gross Intangibles	195,587	195,116
Intangible assets subject to amortization, Accumulated Amortization	(138,830)	(133,689)
Intangible assets subject to amortization, Net Intangibles	$ 56,757	$ 61,427
Intangible assets subject to amortization, Weighted Average Amortization Period (years)	10 years	10 years
Trade Name and Trademarks [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible assets subject to amortization, Gross Intangibles	$ 7,955	$ 7,918
Intangible assets subject to amortization, Accumulated Amortization	(3,743)	(3,225)
Intangible assets subject to amortization, Net Intangibles	$ 4,212	$ 4,693
Intangible assets subject to amortization, Weighted Average Amortization Period (years)	8 years	8 years
Non-Compete Agreements [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible assets subject to amortization, Gross Intangibles	$ 1,051	$ 1,100
Intangible assets subject to amortization, Accumulated Amortization	(872)	(712)
Intangible assets subject to amortization, Net Intangibles	$ 179	$ 388
Intangible assets subject to amortization, Weighted Average Amortization Period (years)	3 years	3 years
Content Library [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible assets subject to amortization, Gross Intangibles	$ 4,835	$ 4,851
Intangible assets subject to amortization, Accumulated Amortization	(965)	(551)
Intangible assets subject to amortization, Net Intangibles	$ 3,870	$ 4,300
Intangible assets subject to amortization, Weighted Average Amortization Period (years)	5 years	5 years
Proprietary Software [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible assets subject to amortization, Gross Intangibles	$ 870	$ 870
Intangible assets subject to amortization, Accumulated Amortization	$ (870)	(835)
Intangible assets subject to amortization, Net Intangibles		$ 35
Intangible assets subject to amortization, Weighted Average Amortization Period (years)	5 years	5 years
Domain Names [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible assets not subject to amortization, Gross Intangibles	$ 162,873	$ 163,132
Intangible assets not subject to amortization, Net Intangibles	$ 162,873	$ 163,132