Subsequent Events	12 Months Ended
Mar. 31, 2018
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events On April 29, 2018, we entered into a Business Combination Agreement with T-Mobile US, Inc. (T-Mobile), Huron Merger Sub LLC, a Delaware limited liability company and a wholly-owned subsidiary of T-Mobile (T-Mobile Merger Company), Superior Merger Sub Corporation, a Delaware corporation and a wholly-owned subsidiary of T-Mobile Merger Company (Merger Sub), Starburst I, Inc., a Delaware corporation (Starburst), Galaxy Investment Holdings, Inc., a Delaware corporation (Galaxy, and together with Starburst, the Softbank US HoldCos) and for the limited purposes set forth therein, Deutsche Telekom AG (Deutsche Telekom), Deutsche Telkom Holding B.V. (DT Holding), and SoftBank Group Corp. Pursuant to the Business Combination Agreement and upon the terms and subject to the conditions described therein, the SoftBank US HoldCos will merge with and into T-Mobile Merger Company, with T-Mobile Merger Company continuing as the surviving entity and as a wholly-owned subsidiary of T-Mobile (the HoldCo Mergers). Immediately following the HoldCo Mergers, the Merger Sub will merge with and into Sprint, with Sprint continuing as the surviving corporation and as a wholly-owned indirect subsidiary of T-Mobile (the Merger and, together with the HoldCo Mergers, the "Merger Transactions"). Pursuant to the Business Combination Agreement, (i) at the effective time of the HoldCo Mergers, all of the issued and outstanding shares of common stock of Galaxy, $0.01 par value per share, and all of the issued and outstanding shares of common stock of Starburst, $0.01 par value per share, held by SoftBank Group Capital Limited, a private limited company incorporated in England and Wales and a wholly-owned subsidiary of SoftBank and the sole stockholder of Galaxy and Starburst (SoftBank UK), will be converted such that SoftBank UK will receive an aggregate number of shares of common stock of T-Mobile, par value $0.00001 per share (T-Mobile Common Stock) equal to the product of (x) 0.10256 (Exchange Ratio) and (y) the aggregate number of shares of common stock of the Company, par value $0.01 (Company Common Stock), held by SoftBank US HoldCos, collectively, immediately prior to the effective time of the HoldCo Mergers, and (ii) the effective time of the Merger, each share of Company Common Stock issued and outstanding immediately prior to the effective time of the Merger (other than shares of Company Common Stock that were held by the SoftBank US HoldCos or are held by the Company as treasury stock) will be converted into the right to receive a number of shares of T-Mobile Common Stock equal to the Exchange Ratio. SoftBank and its affiliates will receive the same amount of T-Mobile Common Stock per share of Company Common Stock as all other Sprint stockholders. Immediately following the Merger Transactions, Deutsche Telekom and SoftBank are expected to hold approximately 42% and 27% of fully-diluted shares of the combined company, respectively, with the remaining approximately 31% of the fully-diluted shares of the combined company held by public stockholders. The consummation of the Merger Transactions and the other transactions contemplated by the Business Combination Agreement (collectively, the Transactions) is subject to obtaining the consent of the holders of a majority of the outstanding shares of Common Stock in favor of the adoption of the Business Combination Agreement (the Company Stockholder Approval). Subsequent to the execution of the Business Combination Agreement, SoftBank entered into a support agreement (the SoftBank Support Agreement), pursuant to which it has agreed to cause SoftBank US, Galaxy and Starburst to deliver a written consent in favor of the adoption of the Business Combination Agreement, which will constitute receipt by the Company of the Company Stockholder Approval. As of April 25, 2018, SoftBank beneficially owned approximately 84.85% of the Company Common Stock outstanding. Under the terms of the SoftBank Support Agreement, SoftBank and its affiliates are generally prohibited from transferring ownership of Company Common Stock prior to the earlier of the consummation of the Merger and the termination of the Business Combination Agreement in accordance with its terms. The consummation of the Transactions is also subject to obtaining the consent of the holders of a majority of the outstanding shares of T-Mobile Common Stock in favor of the issuance of T-Mobile Common Stock in the Merger Transactions (the T-Mobile Stock Issuance Approval) and in favor of the amendment and restatement of T-Mobile's certification of incorporation of its entirety in the form (the T-Mobile Charter Amendment) (collectively, the T-Mobile Stockholder Approval). Subsequent to the execution of the Business Combination Agreement, Deutsche Telekom entered into a support agreement, (the Deutsche Telekom Support Agreement), pursuant to which it has agreed to deliver a written consent in favor of the T-Mobile Stock Issuance and the T-Mobile Charter Amendment, which will constitute receipt by T-Mobile of the T-Mobile Stockholder Approval. As of April 25, 2018, Deutsche Telekom beneficially owned approximately 63.5% of the T-Mobile Common Stock outstanding. Under the terms of the Deutsche Telekom Support Agreement, Deutsche Telekom and its affiliates are generally prohibited from transferring ownership of T-Mobile Common Stock prior to the earlier of the consummation of the Merger and the termination of the Business Combination Agreement in accordance with its terms. The consummation of the Transactions is also subject to the satisfaction or waiver, if legally permitted, of certain other conditions, including, among other things, (i) the accuracy of representations and warranties and performance of covenants of the parties, (ii) the effectiveness of the registration statement for the shares of T-Mobile Common Stock to be issued in the Merger Transactions, and the approval of the listing of such shares on the NASDAQ Global Select Market (NASDAQ), (iii) receipt of certain regulatory approvals, including approvals of the Federal Communications Commission, applicable state public utility commissions and expiration or termination of the applicable waiting period under the Hart-Scott-Rodino Antitrust Improvements Act of 1976 and favorable completion of review by the Committee on Foreign Investments in the United States (CFIUS), (iv) specified minimum credit ratings for T-Mobile on the closing date of the Transactions (after giving effect to the Merger) from at least two of the three credit rating agencies, subject to certain qualifications, and (v) no material adverse effect with respect to the Company or T-Mobile since the date of the Business Combination Agreement. The Business Combination Agreement contains representations and warranties and covenants customary for a transaction of this nature. The Company and SoftBank, and T-Mobile and Deutsche Telekom, are each subject to restrictions on their ability to solicit alternative acquisition proposals and to provide information to, and engage in discussion with, third parties regarding such proposals, except under limited circumstances to permit the Company’s and T-Mobile’s boards of directors to comply with their respective fiduciary duties. Subject to certain exceptions, each of the parties has agreed to use its reasonable best efforts to take or cause to be taken actions necessary to consummate the Transactions, including with respect to obtaining required government approvals. The Business Combination Agreement also contains certain termination rights for both the Company and T-Mobile. In the event that T-Mobile terminates the Business Combination Agreement in connection with a failure to satisfy the closing condition related to the specified minimum credit ratings noted above, then in certain circumstances, T-Mobile may be required to pay Sprint $600 million. Pursuant to the terms of the Business Combination Agreement, T-Mobile, SoftBank and Deutsche Telekom will also enter into an amended and restated stockholders’ agreement (the Stockholders Agreement), which will become effective upon the closing of the Transactions and will provide that the board of directors of the combined company will consist of fourteen members, comprising nine directors designated by Deutsche Telekom (of which at least two will be independent), four directors designated by SoftBank (of which at least two will be independent), and T-Mobile’s chief executive officer. The Stockholders Agreement will also set forth certain consent rights for each of SoftBank and Deutsche Telekom over certain material transactions of T-Mobile and will contain a non-compete which will apply to SoftBank, Deutsche Telekom and their respective affiliates, subject to certain exceptions, until such time as SoftBank’s or Deutsche Telekom’s ownership in T-Mobile has been reduced below an agreed threshold. In addition, pursuant to the terms of the Business Combination Agreement, SoftBank and Deutsche Telekom will enter into a proxy, lock-up and right of first refusal agreement (the PLR Agreement), which will become effective upon the closing of the Transactions, and which will set forth certain rights and obligations in respect to the shares of T-Mobile Common Stock owned by each of SoftBank, Deutsche Telekom and their respective affiliates. Among other terms, these rights and obligations will require SoftBank to agree to vote its shares of T-Mobile Common Stock as directed by Deutsche Telekom and will restrict SoftBank from transferring its shares of T-Mobile Common Stock, subject to certain exceptions set forth in the PLR Agreement. In addition, the PLR Agreement will impose certain restrictions on SoftBank’s and Deutsche Telekom’s ability to transfer their shares of T-Mobile Common Stock in the four year period following the closing of the Transactions and will provide each of SoftBank and Deutsche Telekom with a right of first refusal with respect to proposed transfers of shares of T-Mobile Common Stock by the other party, subject in each case to certain exceptions and limitations set forth in the PLR Agreement. As a result of the PLR Agreement, T-Mobile is expected to continue to be a “Controlled Company” for purposes of NASDAQ rules following consummation of the Merger, which provides T-Mobile with exemptions from certain corporate governance requirements under the NASDAQ rules.

Subsequent Events

On April 29, 2018, we entered into a Business Combination Agreement with T-Mobile US, Inc. (T-Mobile), Huron Merger Sub LLC, a Delaware limited liability company and a wholly-owned subsidiary of T-Mobile (T-Mobile Merger Company), Superior Merger Sub Corporation, a Delaware corporation and a wholly-owned subsidiary of T-Mobile Merger Company (Merger Sub), Starburst I, Inc., a Delaware corporation (Starburst), Galaxy Investment Holdings, Inc., a Delaware corporation (Galaxy, and together with Starburst, the Softbank US HoldCos) and for the limited purposes set forth therein, Deutsche Telekom AG (Deutsche Telekom), Deutsche Telkom Holding B.V. (DT Holding), and SoftBank Group Corp.

Pursuant to the Business Combination Agreement and upon the terms and subject to the conditions described therein, the SoftBank US HoldCos will merge with and into T-Mobile Merger Company, with T-Mobile Merger Company continuing as the surviving entity and as a wholly-owned subsidiary of T-Mobile (the HoldCo Mergers). Immediately following the HoldCo Mergers, the Merger Sub will merge with and into Sprint, with Sprint continuing as the surviving corporation and as a wholly-owned indirect subsidiary of T-Mobile (the Merger and, together with the HoldCo Mergers, the "Merger Transactions"). Pursuant to the Business Combination Agreement, (i) at the effective time of the HoldCo Mergers, all of the issued and outstanding shares of common stock of Galaxy, $0.01 par value per share, and all of the issued and outstanding shares of common stock of Starburst, $0.01 par value per share, held by SoftBank Group Capital Limited, a private limited company incorporated in England and Wales and a wholly-owned subsidiary of SoftBank and the sole stockholder of Galaxy and Starburst (SoftBank UK), will be converted such that SoftBank UK will receive an aggregate number of shares of common stock of T-Mobile, par value $0.00001 per share (T-Mobile Common Stock) equal to the product of (x) 0.10256 (Exchange Ratio) and (y) the aggregate number of shares of common stock of the Company, par value $0.01 (Company Common Stock), held by SoftBank US HoldCos, collectively, immediately prior to the effective time of the HoldCo Mergers, and (ii) the effective time of the Merger, each share of Company Common Stock issued and outstanding immediately prior to the effective time of the Merger (other than shares of Company Common Stock that were held by the SoftBank US HoldCos or are held by the Company as treasury stock) will be converted into the right to receive a number of shares of T-Mobile Common Stock equal to the Exchange Ratio. SoftBank and its affiliates will receive the same amount of T-Mobile Common Stock per share of Company Common Stock as all other Sprint stockholders. Immediately following the Merger Transactions, Deutsche Telekom and SoftBank are expected to hold approximately 42% and 27% of fully-diluted shares of the combined company, respectively, with the remaining approximately 31% of the fully-diluted shares of the combined company held by public stockholders.

The consummation of the Merger Transactions and the other transactions contemplated by the Business Combination Agreement (collectively, the Transactions) is subject to obtaining the consent of the holders of a majority of the outstanding shares of Common Stock in favor of the adoption of the Business Combination Agreement (the Company Stockholder Approval). Subsequent to the execution of the Business Combination Agreement, SoftBank entered into a support agreement (the SoftBank Support Agreement), pursuant to which it has agreed to cause SoftBank US, Galaxy and Starburst to deliver a written consent in favor of the adoption of the Business Combination Agreement, which will constitute receipt by the Company of the Company Stockholder Approval. As of April 25, 2018, SoftBank beneficially owned approximately 84.85% of the Company Common Stock outstanding. Under the terms of the SoftBank Support Agreement, SoftBank and its affiliates are generally prohibited from transferring ownership of Company Common Stock prior to the earlier of the consummation of the Merger and the termination of the Business Combination Agreement in accordance with its terms. The consummation of the Transactions is also subject to obtaining the consent of the holders of a majority of the outstanding shares of T-Mobile Common Stock in favor of the issuance of T-Mobile Common Stock in the Merger Transactions (the T-Mobile Stock Issuance Approval) and in favor of the amendment and restatement of T-Mobile's certification of incorporation of its entirety in the form (the T-Mobile Charter Amendment) (collectively, the T-Mobile Stockholder Approval). Subsequent to the execution of the Business Combination Agreement, Deutsche Telekom entered into a support agreement, (the Deutsche Telekom Support Agreement), pursuant to which it has agreed to deliver a written consent in favor of the T-Mobile Stock Issuance and the T-Mobile Charter Amendment, which will constitute receipt by T-Mobile of the T-Mobile Stockholder Approval. As of April 25, 2018, Deutsche Telekom beneficially owned approximately 63.5% of the T-Mobile Common Stock outstanding. Under the terms of the Deutsche Telekom Support Agreement, Deutsche Telekom and its affiliates are generally prohibited from transferring ownership of T-Mobile Common Stock prior to the earlier of the consummation of the Merger and the termination of the Business Combination Agreement in accordance with its terms.

The consummation of the Transactions is also subject to the satisfaction or waiver, if legally permitted, of certain other conditions, including, among other things, (i) the accuracy of representations and warranties and performance of covenants of the parties, (ii) the effectiveness of the registration statement for the shares of T-Mobile Common Stock to be issued in the Merger Transactions, and the approval of the listing of such shares on the NASDAQ Global Select Market (NASDAQ), (iii) receipt of certain regulatory approvals, including approvals of the Federal Communications Commission, applicable state public utility commissions and expiration or termination of the applicable waiting period under the Hart-Scott-Rodino Antitrust Improvements Act of 1976 and favorable completion of review by the Committee on Foreign Investments in the United States (CFIUS), (iv) specified minimum credit ratings for T-Mobile on the closing date of the Transactions (after giving effect to the Merger) from at least two of the three credit rating agencies, subject to certain qualifications, and (v) no material adverse effect with respect to the Company or T-Mobile since the date of the Business Combination Agreement.

The Business Combination Agreement contains representations and warranties and covenants customary for a transaction of this nature. The Company and SoftBank, and T-Mobile and Deutsche Telekom, are each subject to restrictions on their ability to solicit alternative acquisition proposals and to provide information to, and engage in discussion with, third parties regarding such proposals, except under limited circumstances to permit the Company’s and T-Mobile’s boards of directors to comply with their respective fiduciary duties. Subject to certain exceptions, each of the parties has agreed to use its reasonable best efforts to take or cause to be taken actions necessary to consummate the Transactions, including with respect to obtaining required government approvals. The Business Combination Agreement also contains certain termination rights for both the Company and T-Mobile. In the event that T-Mobile terminates the Business Combination Agreement in connection with a failure to satisfy the closing condition related to the specified minimum credit ratings noted above, then in certain circumstances, T-Mobile may be required to pay Sprint $600 million.

Pursuant to the terms of the Business Combination Agreement, T-Mobile, SoftBank and Deutsche Telekom will also enter into an amended and restated stockholders’ agreement (the Stockholders Agreement), which will become effective upon the closing of the Transactions and will provide that the board of directors of the combined company will consist of fourteen members, comprising nine directors designated by Deutsche Telekom (of which at least two will be independent), four directors designated by SoftBank (of which at least two will be independent), and T-Mobile’s chief executive officer. The Stockholders Agreement will also set forth certain consent rights for each of SoftBank and Deutsche Telekom over certain material transactions of T-Mobile and will contain a non-compete which will apply to SoftBank, Deutsche Telekom and their respective affiliates, subject to certain exceptions, until such time as SoftBank’s or Deutsche Telekom’s ownership in T-Mobile has been reduced below an agreed threshold.

In addition, pursuant to the terms of the Business Combination Agreement, SoftBank and Deutsche Telekom will enter into a proxy, lock-up and right of first refusal agreement (the PLR Agreement), which will become effective upon the closing of the Transactions, and which will set forth certain rights and obligations in respect to the shares of T-Mobile Common Stock owned by each of SoftBank, Deutsche Telekom and their respective affiliates. Among other terms, these rights and obligations will require SoftBank to agree to vote its shares of T-Mobile Common Stock as directed by Deutsche Telekom and will restrict SoftBank from transferring its shares of T-Mobile Common Stock, subject to certain exceptions set forth in the PLR Agreement. In addition, the PLR Agreement will impose certain restrictions on SoftBank’s and Deutsche Telekom’s ability to transfer their shares of T-Mobile Common Stock in the four year period following the closing of the Transactions and will provide each of SoftBank and Deutsche Telekom with a right of first refusal with respect to proposed transfers of shares of T-Mobile Common Stock by the other party, subject in each case to certain exceptions and limitations set forth in the PLR Agreement. As a result of the PLR Agreement, T-Mobile is expected to continue to be a “Controlled Company” for purposes of NASDAQ rules following consummation of the Merger, which provides T-Mobile with exemptions from certain corporate governance requirements under the NASDAQ rules.