Variable Interest Entities (Details) - USD ($) $ in Millions		1 Months Ended	3 Months Ended		12 Months Ended
		Mar. 31, 2015	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2014	Dec. 31, 2015
Assets
Cash and cash equivalents		$ 337	$ 772	$ 337	$ 212	$ 715
Accounts receivable			606			608
Other current assets			23			55
Assets held for sale			26
Licenses			1,808			1,834
Property, plant and equipment, net			2,573			2,649
Other assets and deferred charges			188			172
Liabilities
Current liabilities			723			748
Variable Interest Entities, Other Disclosures
Total winning bid			338
Investments in unconsolidated entities			384			363
Consolidated Variable Interest Entities
Assets
Cash and cash equivalents	[1]		2			1
Accounts receivable	[1]		40
Other current assets	[1]		7
Assets held for sale	[1]		2
Licenses	[1],[2]		652			649
Property, plant and equipment, net	[1]		116			8
Other assets and deferred charges	[1]		9
Total assets	[1]		828			658
Liabilities
Current liabilities	[1]		25
Deferred liabilities and credits	[1]		12			1
Total liabilities	[1]		37			1
Unconsolidated Variable Interest Entities
Variable Interest Entities, Other Disclosures
Investments in unconsolidated entities			5			$ 5
Aggregated Variable Interest Entities
Variable Interest Entities, Other Disclosures
Capital contributions, loans or advances			$ 13	281
Advantage Spectrum L.P.
Variable Interest Entities, Other Disclosures
Federal Communications Commission deposit					$ 60
Total winning bid		338		338
Other auction charges		$ 2		$ 2
Designated entity auction discount		25.00%		25.00%
Licenses won		124		124
King Street Wireless L.P.
Variable Interest Entities, Other Disclosures
Cash distributions paid		$ 60
King Street Wireless, L.P. distribution paid to U.S. Cellular		54
King Street Wireless, L.P. distribution paid to King Street Wireless, Inc.		$ 6

[1] ASU 2015-02 was adopted on a modified retrospective basis and, accordingly, prior year amounts have not been revised to reflect the change in guidance.

[2] Includes payments totaling $338 million made by Advantage Spectrum to the FCC as described above.