Allowance For Doubtful Accounts Writeoffs Net Of Recoveries

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- Definition

Call premiums paid on debt redemptions

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- Definition

Defined Contribution Plan Discretionary Contributions

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Defined Contribution Plan, Employer Matching Contribution, Maximum Match Amount

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Defined Contribution Plan, Employer Matching Contribution, Percent, Additional Contribution

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Defined Contribution Plan, Employer Matching Contribution, Percent, Base Contribution

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Defined Contribution Plan, Employer Matching Contribution, Percent of Match, Additional Contribution

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Defined Contribution Plan, Employer Matching Contribution, Percent of Match, Base Contribution

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- Definition

Defined Contribution Plan Fixed Matching Contributions

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- Definition

Depreciation, equipment rentals

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Installment Billing Maximum Payment Term

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- Definition

Loss on leased devices

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MLS rental payments

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- Definition

Percent Of Fair Value Of Plan Assets Measured at Fair Value

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- Definition

percentage of operating revenues related to universal service fund fees

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- Definition

Pre Tax Share And Non Share Based Compensation Charges

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Revenue, equipment rentals, net

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- Definition

Amount charged to advertising expense for the period, which are expenses incurred with the objective of increasing revenue for a specified brand, product or product line.

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Amount of cash and cash equivalents, and cash and cash equivalents restricted to withdrawal or usage. Excludes amount for disposal group and discontinued operations. Cash includes, but is not limited to, currency on hand, demand deposits with banks or financial institutions, and other accounts with general characteristics of demand deposits. Cash equivalents include, but are not limited to, short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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- Definition

Amount of prior service cost (credit) recognized in net periodic benefit cost (credit) of defined benefit plan.

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- Definition

Amount, before tax, after reclassification adjustment, of increase (decrease) in accumulated other comprehensive income from gain (loss) of defined benefit plan.

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- Definition

Weighted average rate for present value of future retirement benefits cash flows, used to determine benefit obligation of defined benefit plan.

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Weighted average rate of return on plan assets, reflecting average rate of earnings expected on existing plan assets and expected contributions, used to determine net periodic benefit cost of defined benefit plan.

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Amount of actuarial present value of benefits attributed to service rendered by employee for defined benefit plan.

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Amount of contributions expected to be received by defined benefit plan from employer in next fiscal year following latest fiscal year.

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Fair value of assets that have been segregated and restricted to provide pension or postretirement benefits. Assets include, but are not limited to, stocks, bonds, other investments, earnings from investments, and contributions by the employer and employees.

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Amount of funded (unfunded) status of defined benefit plan, measured as difference between fair value of plan assets and benefit obligation. Includes, but is not limited to, overfunded (underfunded) status.

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Percentage of target investment allocation to total plan assets. Includes, but is not limited to, percentage on weighted-average basis if more than one plan.

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Maximum percentage of employee gross pay the employee may contribute to a defined contribution plan.

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- Definition

Unrecognized cost of unvested share-based compensation awards.

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Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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- Definition

The total recognized tax benefit related to compensation cost for equity-based payment arrangements recognized in income during the period.

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- Definition

Amount of cash inflow (outflow) from financing activities, including discontinued operations. Financing activity cash flows include obtaining resources from owners and providing them with a return on, and a return of, their investment; borrowing money and repaying amounts borrowed, or settling the obligation; and obtaining and paying for other resources obtained from creditors on long-term credit.

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Amount of cash inflow (outflow) from operating activities, including discontinued operations. Operating activity cash flows include transactions, adjustments, and changes in value not defined as investing or financing activities.

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- Definition

The cash outflow for payments to acquire rented equipment which is recorded as an asset.

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- Definition

The cash inflow associated with the proceeds from sale and collection of receivables during the period.

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Useful life of long lived, physical assets used in the normal conduct of business and not intended for resale, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Examples include, but not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

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- Definition

The cumulative amount of the reporting entity's undistributed earnings or deficit.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition

Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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- Definition

The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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- Definition

The estimated dividend rate (a percentage of the share price) to be paid (expected dividends) to holders of the underlying shares over the option's term.

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The estimated measure of the maximum percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period.

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The estimated measure of the minimum percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period.

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The maximum risk-free interest rate assumption that is used in valuing an option on its own shares.

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The minimum risk-free interest rate assumption that is used in valuing an option on its own shares.

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- Definition

Number of equity instruments other than options outstanding, including both vested and non-vested instruments.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

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The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan.

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Net number of share options (or share units) granted during the period.

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The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

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Number of options outstanding, including both vested and non-vested options.

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Percentage of vesting of share-based compensation awards.

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Period from grant date that an equity-based award expires, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Expected term of share-based compensation awards, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Summary of Significant Accounting Policies and Other Information (Details) - USD ($) $ / shares in Units, shares in Millions	3 Months Ended			9 Months Ended	12 Months Ended
	Jun. 30, 2017	Mar. 31, 2017	Mar. 31, 2015	Dec. 31, 2016	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2013	Apr. 01, 2018	Jan. 01, 2018
Revenue, equipment rentals, net						$ 4,048,000,000	$ 3,295,000,000	$ 1,838,000,000
Loss on leased devices							(481,000,000)	(321,000,000)
MLS rental payments							(494,000,000)	(277,000,000)
Depreciation, equipment rentals						3,792,000,000	3,116,000,000	1,781,000,000
Allowance For Doubtful Accounts Writeoffs Net Of Recoveries						451,000,000	371,000,000	612,000,000
Defined Benefit Plan, Fair Value of Plan Assets						1,400,000,000
Defined Benefit Plan, Benefit Obligation		$ 2,200,000,000				2,200,000,000	2,200,000,000
Defined Benefit Plan, Funded (Unfunded) Status of Plan						(800,000,000)
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), after Reclassification Adjustment, before Tax						$ (30,000,000)	$ 35,000,000	$ (29,000,000)
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate		4.30%	4.20%			4.10%	4.30%	4.30%
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)						$ 0	$ 0	$ (9,000,000)
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Rate of Return on Plan Assets						7.50%	7.75%
Defined Contribution Plan, Employer Matching Contribution, Percent of Match, Base Contribution		50.00%		100.00%		100.00%	50.00%	100.00%
Defined Contribution Plan, Employer Matching Contribution, Percent, Base Contribution		4.00%		3.00%		4.00%		3.00%
Defined Contribution Plan, Employer Matching Contribution, Percent of Match, Additional Contribution				50.00%				50.00%
Defined Contribution Plan, Employer Matching Contribution, Percent, Additional Contribution				2.00%				2.00%
Defined Contribution Plan, Maximum Annual Contributions Per Employee, Percent				4.00%				4.00%
Defined Contribution Plan Fixed Matching Contributions						$ 38,000,000	$ 28,000,000	$ 54,000,000
Defined Contribution Plan Discretionary Contributions						14,000,000
Defined Contribution Plan, Employer Matching Contribution, Maximum Match Amount						$ 500
Percentage of Operating Revenues Related to Universal Service Fund Fees						2.00%	2.00%	2.00%
Installment Billing Maximum Payment Term						24 months
Number of shares available and reserved for future grants under the 2007 Plan and ESPP						201
Pre Tax Share And Non Share Based Compensation Charges						$ 182,000,000	$ 93,000,000	$ 75,000,000
Employee Service Share-based Compensation, Tax Benefit from Compensation Expense						65,000,000	33,000,000	20,000,000
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized						$ 190,000,000
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition						1 year 11 months 24 days
Advertising Expense						$ 1,300,000,000	1,100,000,000	1,300,000,000
Retained Earnings (Accumulated Deficit)		$ (8,584,000,000)				(1,255,000,000)	(8,584,000,000)
Proceeds from Sale and Collection of Receivables						1,140,000,000	10,498,000,000	7,925,000,000
Payments to Acquire Equipment on Lease						7,461,000,000	4,976,000,000	5,898,000,000
Call premiums paid on debt redemptions						131,000,000	0	0
Net cash provided by (used in) operating activities						10,062,000,000	(3,290,000,000)	(423,000,000)
Net cash provided by (used in) financing activities						210,000,000	(5,286,000,000)	(469,000,000)
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents		2,942,000,000	$ 4,010,000,000			$ 6,659,000,000	2,942,000,000	2,641,000,000
Building and Building Improvements [Member] \| Minimum [Member]
Property, Plant and Equipment, Useful Life						3 years
Building and Building Improvements [Member] \| Maximum [Member]
Property, Plant and Equipment, Useful Life						30 years
Non-network Internal Use Software Office Equipment, Leased Devices And Other [Member] \| Minimum [Member]
Property, Plant and Equipment, Useful Life						3 years
Non-network Internal Use Software Office Equipment, Leased Devices And Other [Member] \| Maximum [Member]
Property, Plant and Equipment, Useful Life						12 years
Network and Non-network Software [Member] \| Minimum [Member]
Property, Plant and Equipment, Useful Life						3 years
Network and Non-network Software [Member] \| Maximum [Member]
Property, Plant and Equipment, Useful Life						5 years
U.S. Equity Securities [Member]
Defined Benefit Plan, Target Allocation Percentage of Assets, Equity Securities						38.00%
International Equity Securities [Member] [Member]
Defined Benefit Plan, Target Allocation Percentage of Assets, Equity Securities						16.00%
Fixed Income Investments [Member]
Defined Benefit Plan, Target Allocation Percentage of Assets, Equity Securities						37.00%
Fixed Income Securities [Member]
Defined Benefit Plan, Target Allocation Percentage of Assets, Equity Securities						28.00%
Real Estate Investment [Member]
Defined Benefit Plan, Target Allocation Percentage of Assets, Equity Securities						9.00%
Other Investment Companies [Member]
Defined Benefit Plan, Target Allocation Percentage of Assets, Equity Securities						9.00%
Quoted prices in active markets [Member]
Investment Owned, Percent of Net Assets						26.00%
Observable [Member]
Investment Owned, Percent of Net Assets						64.00%
Unobservable [Member]
Investment Owned, Percent of Net Assets						10.00%
Employee Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Net of Forfeitures						3
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value						$ 3.98
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate, Minimum						1.93%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate, Maximum						2.65%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate, Minimum						41.90%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate, Maximum						51.80%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Rate						0.00%
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period						3 years
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Weighted Average Remaining Contractual Term						10 years
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number						29
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Number						18
Employee Stock Option [Member] \| Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Term						5 years 6 months
Employee Stock Option [Member] \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Term						6 years 6 months
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period						20
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value						$ 6.90
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding, Number						78
Restricted Stock Units (RSUs) [Member] \| Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period						1 year
Restricted Stock Units (RSUs) [Member] \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period						3 years
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate, Minimum						1.79%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate, Maximum						2.42%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate, Minimum						41.90%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate, Maximum						51.80%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Rate						0.00%
Tranche one [Member] \| Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period						2 years
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage						50.00%
Tranche two [Member] \| Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period						4 years
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage						50.00%
Share-based Compensation Award, Tranche Three [Member] \| Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period						5 years
Scenario, Forecast [Member]
Defined Benefit Plan, Estimated Future Employer Contributions in Next Fiscal Year					$ 82,000,000
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Rate of Return on Plan Assets					7.25%
Defined Contribution Plan, Employer Matching Contribution, Percent, Base Contribution					3.00%
Revenue from Contract with Customer [Member] \| Scenario, Forecast [Member] \| Minimum [Member]
Retained Earnings (Accumulated Deficit)										$ 1,500,000,000
Revenue from Contract with Customer [Member] \| Scenario, Forecast [Member] \| Maximum [Member]
Retained Earnings (Accumulated Deficit)										1,800,000,000
Capitalized Contract Cost [Domain] \| Scenario, Forecast [Member] \| Minimum [Member]
Retained Earnings (Accumulated Deficit)										1,100,000,000
Capitalized Contract Cost [Domain] \| Scenario, Forecast [Member] \| Maximum [Member]
Retained Earnings (Accumulated Deficit)										1,300,000,000
Adjustments for New Accounting Pronouncement [Member]
Payments to Acquire Equipment on Lease							3,100,000,000	$ 3,600,000,000
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents		$ 72,000,000					$ 72,000,000
Adjustments for New Accounting Pronouncement [Member] \| Scenario, Forecast [Member] \| Minimum [Member]
Retained Earnings (Accumulated Deficit)										400,000,000
Adjustments for New Accounting Pronouncement [Member] \| Scenario, Forecast [Member] \| Maximum [Member]
Retained Earnings (Accumulated Deficit)										$ 500,000,000
Reclassification out of Accumulated Other Comprehensive Income [Domain]
Retained Earnings (Accumulated Deficit)											$ 60,000,000
Accounting Standards Update 2016-15 [Member]
Net cash provided by (used in) operating activities	$ 129,000,000
Net cash provided by (used in) financing activities	$ 129,000,000