Segment Data (Segment Reporting Information Disclosure) (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Segment Reporting Information [Line Items]
Revenues		$ 423,363	$ 399,769
Cost of revenues		110,970	102,595
Operating profit		312,393	297,174
Selling, general, and administrative	[1]	34,223	30,406
Acquisition related adjustments and expenses		2,969	3,182
Asset impairment and decommission costs		8,351	6,183
Depreciation, amortization and accretion		159,031	159,801
Operating income		107,819	97,602
Other expense (principally interest expense and other expense)		(66,823)	(41,758)
Income before provision for income taxes		40,996	55,844
Cash capital expenditures		78,398	128,165
Assets		7,297,450		$ 7,360,945
Domestic Site Leasing [Member]
Segment Reporting Information [Line Items]
Revenues		321,130	315,230
Cost of revenues		65,427	64,475
Operating profit		255,703	250,755
Selling, general, and administrative		19,356	17,998
Acquisition related adjustments and expenses		1,901	1,842
Asset impairment and decommission costs		7,430	6,021
Depreciation, amortization and accretion		123,896	131,393
Operating income		103,120	93,501
Cash capital expenditures		50,433	105,353
Assets		5,313,286		5,396,394
International Site Leasing [Member]
Segment Reporting Information [Line Items]
Revenues		76,420	59,220
Cost of revenues		23,955	18,287
Operating profit		52,465	40,933
Selling, general, and administrative		5,959	4,385
Acquisition related adjustments and expenses		1,068	1,340
Asset impairment and decommission costs		816	162
Depreciation, amortization and accretion		32,825	26,877
Operating income		11,797	8,169
Cash capital expenditures		26,890	21,380
Assets		1,856,435		1,839,703
Site Development [Member]
Segment Reporting Information [Line Items]
Revenues		25,813	25,319
Cost of revenues		21,588	19,833
Operating profit		4,225	5,486
Selling, general, and administrative		3,617	3,537
Asset impairment and decommission costs		105
Depreciation, amortization and accretion		711	1,025
Operating income		(208)	924
Cash capital expenditures		133	556
Assets		37,787		43,769
Not Identified by Segment [Member]
Segment Reporting Information [Line Items]
Selling, general, and administrative		5,291	4,486
Depreciation, amortization and accretion		1,599	506
Operating income		(6,890)	(4,992)
Other expense (principally interest expense and other expense)		(66,823)	(41,758)
Cash capital expenditures		942	$ 876
Assets		$ 89,942		$ 81,079

[1] Includes non-cash compensation of $8,826 and $7,686 for the three months ended March 31, 2017 and 2016, respectively.