Goodwill and Other Intangible Assets - Summary of Intangible Assets (Detail) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 3,251,699	$ 3,174,658
Accumulated Amortization	2,342,191	2,260,212
Goodwill gross carrying amount	2,180,455	2,165,864
Goodwill accumulated amortization	253,536	253,536
Customer lists and contracts
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	655,843	645,739
Accumulated Amortization	$ 580,671	563,135
Customer lists and contracts | Minimum
Finite-Lived Intangible Assets [Line Items]
Estimated Life (Years)	7 years
Customer lists and contracts | Maximum
Finite-Lived Intangible Assets [Line Items]
Estimated Life (Years)	10 years
Non-competition agreements
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 66,596	66,156
Accumulated Amortization	$ 64,857	64,647
Non-competition agreements | Minimum
Finite-Lived Intangible Assets [Line Items]
Estimated Life (Years)	3 years
Non-competition agreements | Maximum
Finite-Lived Intangible Assets [Line Items]
Estimated Life (Years)	15 years
Site locations
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 2,479,103	2,412,745
Accumulated Amortization	$ 1,657,456	1,593,805
Site locations | Maximum
Finite-Lived Intangible Assets [Line Items]
Estimated Life (Years)	15 years
Other Intangible Assets
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 50,157	50,018
Accumulated Amortization	$ 39,207	$ 38,625
Other Intangible Assets | Minimum
Finite-Lived Intangible Assets [Line Items]
Estimated Life (Years)	2 years
Other Intangible Assets | Maximum
Finite-Lived Intangible Assets [Line Items]
Estimated Life (Years)	15 years