Goodwill and Other Intangible Assets - Summary of Intangible Assets (Detail) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Dec. 31, 2017
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 2,742,525	$ 2,769,332
Accumulated Amortization	1,988,605	1,972,984
Goodwill gross carrying amount	1,990,893	1,993,990
Goodwill accumulated amortization	253,536	253,536
Customer Lists and Contracts [Member]
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	578,003	586,055
Accumulated Amortization	$ 505,760	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	$ 65,561	65,477
Accumulated Amortization	$ 64,004	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	$ 2,053,107	2,072,059
Accumulated Amortization	$ 1,386,852	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	$ 45,854	45,741
Accumulated Amortization	$ 31,989	$ 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