Goodwill and Other Intangible Assets - Summary of Intangible Assets (Detail) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2015	Dec. 31, 2014
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 2,186,968	$ 2,108,541
Accumulated Amortization	1,789,777	1,741,556
Goodwill gross carrying amount	1,796,797	1,766,304
Goodwill accumulated amortization	253,536	253,536
Customer Lists and Contracts [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	511,219	499,310
Accumulated Amortization	$ 475,150	470,170
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	$ 64,411	64,062
Accumulated Amortization	$ 63,388	63,192
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	$ 1,597,330	1,531,161
Accumulated Amortization	$ 1,237,720	1,194,709
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	$ 14,008	14,008
Accumulated Amortization	$ 13,519	$ 13,485
Other [Member] | Minimum [Member]
Finite-Lived Intangible Assets [Line Items]
Estimated Life (Years)	5 years
Other [Member] | Maximum [Member]
Finite-Lived Intangible Assets [Line Items]
Estimated Life (Years)	15 years