Goodwill and Other Intangible Assets - Summary of Intangible Assets (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 2,736,130	$ 2,769,332
Accumulated Amortization	1,965,760	1,972,984
Goodwill gross carrying amount	1,990,938	1,993,990
Goodwill accumulated amortization	253,536	253,536
Customer Lists and Contracts [Member]
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	577,351	586,055
Accumulated Amortization	$ 501,494	505,778
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	$ 65,482	65,477
Accumulated Amortization	$ 63,941	63,924
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	$ 2,047,492	2,072,059
Accumulated Amortization	$ 1,369,167	1,372,954
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	$ 45,805	45,741
Accumulated Amortization	$ 31,158	$ 30,328
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