Consolidated Statements of Cash Flows - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating activities
Net income		$ 3,468	$ 2,888	$ 4,536
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation and amortization		6,616	6,486	5,984
Stock-based compensation expense		495	424	306
Deferred income tax expense (benefit)		1,091	980	(1,404)
Bad debt expense		307	297	388
Losses from sales of receivables		130	157	299
Deferred rent expense		0	26	76
Losses on redemption of debt		19	122	86
Gains on disposal of spectrum licenses		0	0	(235)
Changes in operating assets and liabilities
Accounts receivable		(3,709)	(4,617)	(3,931)
Equipment installment plan receivables		(1,015)	(1,598)	(1,812)
Inventories		(617)	(201)	(844)
Operating lease right-of-use assets		1,896
Other current and long-term assets		(144)	(181)	(575)
Accounts payable and accrued liabilities		17	(867)	1,079
Short and long-term operating lease liabilities		(2,131)
Other current and long-term liabilities		144	(69)	(233)
Other, net		257	52	111
Net cash provided by operating activities		6,824	3,899	3,831
Investing activities
Purchases of property and equipment, including capitalized interest of $473, $362 and $136		(6,391)	(5,541)	(5,237)
Purchases of spectrum licenses and other intangible assets, including deposits		(967)	(127)	(5,828)
Proceeds from sales of tower sites		38	0	0
Proceeds related to beneficial interests in securitization transactions		3,876	5,406	4,319
Net cash related to derivative contracts under collateral exchange arrangements		(632)	0	0
Acquisition of companies, net of cash acquired		(31)	(338)	0
Other, net		(18)	21	1
Net cash used in investing activities		(4,125)	(579)	(6,745)
Financing activities
Proceeds from issuance of long-term debt		0	2,494	10,480
Proceeds from borrowing on revolving credit facility		2,340	6,265	2,910
Repayments of revolving credit facility		(2,340)	(6,265)	(2,910)
Repayments of financing lease obligations		(798)	(700)	(486)
Repayments of short-term debt for purchases of inventory, property and equipment, net		(775)	(300)	(300)
Repayments of long-term debt		(600)	(3,349)	(10,230)
Repurchases of common stock		0	(1,071)	(427)
Tax withholdings on share-based awards		(156)	(146)	(166)
Dividends on preferred stock		0	0	(55)
Cash payments for debt prepayment or debt extinguishment costs		(28)	(212)	(188)
Other, net		(17)	(52)	5
Net cash used in financing activities		(2,374)	(3,336)	(1,367)
Change in cash and cash equivalents		325	(16)	(4,281)
Cash and cash equivalents
Beginning of period		1,203	1,219	5,500
End of period		1,528	1,203	1,219
Supplemental disclosure of cash flow information
Interest payments, net of amounts capitalized		1,128	1,525	2,028
Operating lease payments	[1]	2,783
Income tax payments		88	51	31
Non-cash investing and financing activities
Non-cash beneficial interest obtained in exchange for securitized receivables		6,509	4,972	4,063
(Decrease) increase in accounts payable for purchases of property and equipment		(935)	65	313
Leased devices transferred from inventory to property and equipment		1,006	1,011	1,131
Returned leased devices transferred from property and equipment to inventory		(267)	(326)	(742)
Short-term debt assumed for financing of property and equipment		800	291	292
Operating lease right-of-use assets obtained in exchange for lease obligations		3,621
Financing lease right-of-use assets obtained in exchange for lease obligations		$ 1,041	$ 885	$ 887

[1] On January 1, 2019, we adopted Accounting Standards Update (“ASU”) 2016-02, “Leases (Topic 842),” which requires certain supplemental cash flow disclosures. Where these disclosures or a comparable figure were not required under the former lease standard, we have not retrospectively presented historical amounts. See Note 1 – Summary of Significant Accounting Policies for additional details.