Concentration Of Credit Risk (Tables)

12 Months Ended

Dec. 31, 2017

Concentration Of Credit Risk [Abstract]

Summary Of Significant Customers And Percentage Of Total Revenue For Specified Time Periods Derived From Such Customers

The following is a list of significant customers (representing at least 10% of revenue for any period reported) and the percentage of total revenue for the specified time periods derived from such customers:

	For the year ended December 31,
Percentage of Total Revenues	2017	2016	2015
AT&T Wireless	25.0%	25.7%	24.2%
T-Mobile	16.5%	17.0%	16.0%
Verizon Wireless	15.2%	15.2%	13.8%
Sprint	15.1%	16.1%	19.6%

The Company’s site leasing and site development segments derive revenue from these customers. Client percentages of total revenue in each of the segments are as follows:

	For the year ended December 31,
Percentage of Domestic Site Leasing Revenue	2017	2016	2015
AT&T Wireless	32.7%	32.7%	31.9%
T-Mobile	19.7%	19.6%	19.0%
Verizon Wireless	19.0%	18.2%	16.3%
Sprint	18.9%	19.8%	22.3%
	For the year ended December 31,
Percentage of International Site Leasing Revenue	2017	2016	2015
Oi S.A.	42.2%	43.9%	48.8%
Telefonica	25.7%	26.4%	24.7%
Claro	10.0%	9.4%	8.0%

	For the year ended December 31,
Percentage of Site Development Revenue	2017	2016	2015
T-Mobile	26.9%	28.4%	17.6%
Sprint	12.9%	11.7%	28.5%
Verizon Wireless	12.8%	16.5%	14.8%
Nokia, Inc.	10.1%	7.1%	6.3%
Ericsson, Inc.	7.4%	5.0%	15.3%