Operating Segments Operating Segments Table (Details) $ in Millions		3 Months Ended
		Mar. 31, 2018 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2017 USD ($)
Segment Reporting Information [Line Items]
Tower Count		40,000
Segment site rental revenues		$ 1,153	$ 857
Segment network services and other revenues		$ 146	159
Fiber Miles		60,000
Segment revenues		$ 1,299	1,016
Segment site rental cost of operations	[1]	347	265
Segment network services and other cost of operations	[1]	86	99
Segment general and administrative expenses		134	101
Stock-based compensation expense		23	22
Depreciation, Amortization and Accretion, Net		374	289
Interest expense and amortization of deferred financing costs		160	134
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest		118	123
Capital expenditures		370	262
Total Assets		32,250		$ 32,229
Amortization of prepaid lease purchase price adjustments		5
Segment cost of operations share-based compensation [Member]
Segment Reporting Information [Line Items]
Stock-based compensation expense		7	5
Towers [Member]
Segment Reporting Information [Line Items]
Segment site rental revenues		764	717
Segment network services and other revenues		142	150
Segment revenues		906	867
Segment site rental cost of operations		211	209
Segment network services and other cost of operations		82	89
Segment cost of operations	[2]	293	298
Segment site rental gross margin		553	508
Segment network services gross margin		60	61
Segment general and administrative expenses	[2]	26	24
Segment Operating Profit		587	545
Capital expenditures		96	101
Total Assets		17,868	18,255
Small Cells [Member]
Segment Reporting Information [Line Items]
Segment site rental revenues		389	140
Segment network services and other revenues		4	9
Segment revenues		393	149
Segment site rental cost of operations		126	47
Segment network services and other cost of operations		2	8
Segment cost of operations	[2]	128	55
Segment site rental gross margin		263	93
Segment network services gross margin		2	1
Segment general and administrative expenses	[2]	43	18
Segment Operating Profit		222	76
Capital expenditures		262	154
Total Assets		13,883	5,054
Consolidated Total [Member]
Segment Reporting Information [Line Items]
Segment site rental revenues		1,153	857
Segment network services and other revenues		146	159
Segment revenues		1,299	1,016
Segment site rental cost of operations		337	256
Segment network services and other cost of operations		84	97
Segment cost of operations	[2]	421	353
Segment site rental gross margin		816	601
Segment network services gross margin		62	62
Segment general and administrative expenses	[2]	69	42
Segment Operating Profit		809	621
Stock-based compensation expense		26	25
Depreciation, Amortization and Accretion, Net		374	289
Interest expense and amortization of deferred financing costs		160	134
Other expenses to reconcile to income (loss) from continuing operations before income taxes		85	11
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest		118	123
Capital expenditures		370	262
Total Assets		32,250	23,777
Other [Member]
Segment Reporting Information [Line Items]
Segment general and administrative expenses	[2]	46	39
Segment Operating Profit
Stock-based compensation expense		26	25
Depreciation, Amortization and Accretion, Net		374	289
Interest expense and amortization of deferred financing costs		160	134
Other expenses to reconcile to income (loss) from continuing operations before income taxes		85
Capital expenditures		12	7
Total Assets		499	468
Segment G&A share-based compensation [Member]
Segment Reporting Information [Line Items]
Stock-based compensation expense		$ 19	$ 20

[1] Exclusive of depreciation, amortization and accretion shown separately.

[2] Segment cost of operations excludes (1) stock-based compensation expense of $7 million and $5 million for the three months ended March 31, 2018 and 2017, respectively, and (2) prepaid lease purchase price adjustments of $5 million for both of the three months ended March 31, 2018 and 2017. General and administrative expenses exclude stock-based compensation expense of $19 million and $20 million for the three months ended March 31, 2018 and 2017, respectively.