Tower Obligations - Sale Leaseback Transaction (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Sale Leaseback Transaction [Line Items]
Failed sale-leasebacks	$ 198	$ 329
Failed Sale Leaseback Transaction, Tower Obligations
Sale Leaseback Transaction [Line Items]
Failed sale-leasebacks	$ 2,236	$ 2,557

The net book value of the asset(s) sold in connection with the sale of the property to another party and lease back to the seller.

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Name:	us-gaap_SaleLeasebackTransactionNetBookValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant