Schedule III - Schedule of Real Estate and Accumulated Depreciation (Reconciliation of Carrying Amount of Real Estate Investments) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Schedule III - Schedule of Real Estate and Accumulated Depreciation [Abstract]
Gross amount at beginning	$ 5,561,005	$ 5,340,858	$ 5,079,660
Acquisitions	111,734	131,686	112,979
Construction and related costs on new builds	48,975	54,237	70,361
Augmentation and tower upgrades	63,998	49,201	43,288
Land buyouts and other assets	39,298	37,032	41,657
Tower maintenance	28,960	30,048	29,391
Total additions	292,965	302,204	297,676
Cost of real estate sold or disposed	(856)	(1,083)	(1,027)
Impairment	(9,587)	(17,130)	(34,101)
Other	(10,189)	(63,844)	(1,350)
Total deductions	(20,632)	(82,057)	(36,478)
Balance at end	$ 5,833,338	$ 5,561,005	$ 5,340,858