Concentration Of Credit Risk (Summary Of Significant Customers And Percentage Of Total Revenue For Specified Time Periods Derived From Such Customers) (Detail)	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Ericsson, Inc [Member] | Site Development Consulting [Member]
Concentration Risk [Line Items]
Concentration risk percentage of revenue	17.60%	0.30%	20.60%	0.90%
Ericsson, Inc [Member] | Site Development Construction [Member]
Concentration Risk [Line Items]
Concentration risk percentage of revenue	26.90%	6.40%	19.20%	8.50%
Alcatel-Lucent [Member] | Site Development Consulting [Member]
Concentration Risk [Line Items]
Concentration risk percentage of revenue	10.70%	0.00%	10.00%	0.00%
Verizon [Member] | Site Development Consulting [Member]
Concentration Risk [Line Items]
Concentration risk percentage of revenue	9.80%	18.00%	12.00%	17.40%
Verizon [Member] | Site Leasing [Member]
Concentration Risk [Line Items]
Concentration risk percentage of revenue	13.30%	15.70%	13.70%	15.60%
Nsoro Mastec [Member] | Site Development Consulting [Member]
Concentration Risk [Line Items]
Concentration risk percentage of revenue	5.90%	4.00%	6.10%	10.70%
Nsoro Mastec [Member] | Site Development Construction [Member]
Concentration Risk [Line Items]
Concentration risk percentage of revenue	23.50%	48.00%	26.50%	43.40%
T-Mobile [Member] | Site Development Construction [Member]
Concentration Risk [Line Items]
Concentration risk percentage of revenue	2.60%	10.30%	5.70%	9.30%
T-Mobile [Member] | Site Leasing [Member]
Concentration Risk [Line Items]
Concentration risk percentage of revenue	15.40%	11.20%	13.90%	11.30%
Overland Contracting [Member] | Site Development Construction [Member]
Concentration Risk [Line Items]
Concentration risk percentage of revenue	10.90%	5.60%	9.50%	7.00%
AT&T [Member] | Site Leasing [Member]
Concentration Risk [Line Items]
Concentration risk percentage of revenue	23.00%	27.00%	23.80%	27.00%
Sprint [Member] | Site Leasing [Member]
Concentration Risk [Line Items]
Concentration risk percentage of revenue	22.00%	21.80%	22.70%	22.10%