Goodwill and Other Intangible Assets - Summary of Intangible Assets (Detail) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Dec. 31, 2018
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 3,045,673	$ 2,950,906
Accumulated Amortization	2,091,963	2,035,453
Goodwill gross carrying amount	2,136,089	2,172,922
Goodwill accumulated amortization	253,536	253,536
Customer Lists and Contracts [Member]
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	627,836	610,376
Accumulated Amortization	$ 527,034	514,928
Customer Lists and Contracts [Member] | Minimum [Member]
Finite Lived Intangible Assets [Line Items]
Estimated Life (Years)	7 years
Customer Lists and Contracts [Member] | Maximum [Member]
Finite Lived Intangible Assets [Line Items]
Estimated Life (Years)	10 years
Non-competition Agreements [Member]
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 65,924	65,771
Accumulated Amortization	$ 64,247	64,119
Non-competition Agreements [Member] | Minimum [Member]
Finite Lived Intangible Assets [Line Items]
Estimated Life (Years)	3 years
Non-competition Agreements [Member] | Maximum [Member]
Finite Lived Intangible Assets [Line Items]
Estimated Life (Years)	15 years
Site Locations [Member]
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 2,305,338	2,228,767
Accumulated Amortization	$ 1,465,416	1,422,794
Site Locations [Member] | Maximum [Member]
Finite Lived Intangible Assets [Line Items]
Estimated Life (Years)	15 years
Other [Member]
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 46,575	45,992
Accumulated Amortization	$ 35,266	$ 33,612
Other [Member] | Minimum [Member]
Finite Lived Intangible Assets [Line Items]
Estimated Life (Years)	2 years
Other [Member] | Maximum [Member]
Finite Lived Intangible Assets [Line Items]
Estimated Life (Years)	15 years