Intangible Assets, Net (Gross and Net Carrying Amounts for each Major Class of Intangible Assets) (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	$ 6,548,716	$ 6,647,824
Accumulated amortization	(3,564,618)	(3,491,674)
Net book value	2,984,098	3,156,150
Current Contract Intangibles [Member]
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	4,794,137	4,876,880
Accumulated amortization	(2,520,675)	(2,471,438)
Net book value	2,273,462	2,405,442
Network Location Intangibles [Member]
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	1,754,579	1,770,944
Accumulated amortization	(1,043,943)	(1,020,236)
Net book value	$ 710,636	$ 750,708