Acquisitions (Schedule Of Acquisition Capital Expenditures) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Acquisitions [Abstract]
Acquisitions of towers and related intangible assets	$ 392,902	$ 214,686	$ 525,802
Land buyouts and other assets	48,645	62,149	83,728
Total cash acquisition capital expenditures	441,547	276,835	609,530
Acquisition costs paid through the issuance of common stock	$ 63,300
Common stock issued for acquisition costs	487,963
Ground lease extensions	$ 18,800	$ 14,100	$ 16,300