Acquisitions (Schedule Of Acquisition Activity) (Details) - item	1 Months Ended		12 Months Ended
	Dec. 31, 2017	Nov. 30, 2014	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Acquisitions [Abstract]
Tower acquisitions (number of towers)	941	1,641	1,425	531	893