Commitments and Contingencies	3 Months Ended
Mar. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies There were no significant changes to the contractual obligations reported in the 2017 Form 10-K other than those which occur in the normal course of business. In connection with various contracts and agreements, the Company has agreed to indemnify counterparties against certain third party claims relating to the infringement of intellectual property rights and other items. Generally, such indemnification obligations do not apply in situations in which the counterparties are grossly negligent, engage in willful misconduct, or act in bad faith. Based on the Company’s historical experience and the estimated probability of future loss, the Company has determined that the fair value of such indemnifications is not material to its consolidated financial position or results of operations. From time to time, the Company is involved in litigation and other proceedings, including matters related to commercial and intellectual property disputes, as well as trade, regulatory and other claims related to its business. Other than as described below, the Company believes that all current proceedings are routine in nature and incidental to the conduct of its business, and that the ultimate resolution of any such proceedings will not have a material adverse effect on its consolidated financial position, results of operations or cash flows. Securities Class Action On March 23, 2017, three separate securities cases previously filed against the Company in the United States District Court for the District of Maryland (the “Court”) were consolidated under the caption In re Under Armour Securities Litigation, Case No. 17-cv-00388-RDB (the “Consolidated Action”). On August 4, 2017, the lead plaintiff in the Consolidated Action, North East Scotland Pension Fund, joined by named plaintiff Bucks County Employees Retirement Fund, filed a consolidated amended complaint (the “Amended Complaint”) against the Company, the Company’s Chief Executive Officer and former Chief Financial Officers, Lawrence Molloy and Brad Dickerson. The Amended Complaint alleges violations of Section 10(b) (and Rule 10b-5) of the Securities Exchange Act of 1934, as amended (the “Exchange Act”) and Section 20(a) control person liability under the Exchange Act against the officers named in the Amended Complaint, claiming that the defendants made material misstatements and omissions regarding, among other things, the Company's growth and consumer demand for certain of the Company's products. The class period identified in the Amended Complaint is September 16, 2015 through January 30, 2017. The Amended Complaint also asserts claims under Sections 11 and 15 of the Securities Act of 1933, as amended (the “Securities Act”), in connection with the Company’s public offering of senior unsecured notes in June 2016. The Securities Act claims are asserted against the Company, the Company’s Chief Executive Officer, Mr. Molloy, the Company’s directors who signed the registration statement pursuant to which the offering was made and the underwriters that participated in the offering. The Amended Complaint alleges that the offering materials utilized in connection with the offering contained false and/or misleading statements and omissions regarding, among other things, the Company’s growth and consumer demand for certain of the Company’s products. On November 9, 2017, the Company and the other defendants filed a motion to dismiss the Amended Complaint, which is still pending with the Court. The Company believes that the claims asserted in the Consolidated Action are without merit and intends to defend the lawsuit vigorously. However, because of the inherent uncertainty as to the outcome of this proceeding, the Company is unable at this time to estimate the possible impact of the outcome of this matter. Derivative Complaints In April 2018, two purported stockholders filed separate stockholder derivative complaints in the United States District Court for the District of Maryland (the “Derivative Complaints”). The Derivative Complaints were brought against Kevin Plank (the Company’s Chairman and Chief Executive Officer) and certain other members of the Company’s Board of Directors and name the Company as a nominal defendant. The Derivative Complaints make allegations related to the Company’s purchase of certain parcels of land from entities controlled by Mr. Plank (through Sagamore Development Company, LLC ("Sagamore")), as well as other alleged related party transactions. Sagamore purchased these parcels in 2014. Its total investment in the parcels was approximately $72.0 million, which included the initial $35.0 million purchase price for the property, an additional $30.6 million to terminate a lease encumbering the property and approximately $6.4 million of development costs. As previously disclosed, in June 2016, the Company purchased the unencumbered parcels for $70.3 million in order to further expand the Company’s corporate headquarters to accommodate its growth needs. The Company negotiated a purchase price for the parcels that it determined represented the fair market value of the parcels and approximated the cost to the seller to purchase and develop the parcels. In connection with its evaluation of the potential purchase, the Company engaged an independent third-party to appraise the fair market value of the parcels, and the Audit Committee of the Company’s Board of Directors engaged its own independent appraisal firm to assess the parcels. The Audit Committee determined that the terms of the purchase were reasonable and fair, and the transaction was approved by the Audit Committee in accordance with the Company’s policy on transactions with related persons. In Mioduszewski v. Plank, et al., filed on April 16, 2018, the complaint asserts that Mr. Plank and the director defendants breached their fiduciary duties in connection with the purchase of the parcels and other alleged related party transactions and that the director defendants aided and abetted Mr. Plank’s alleged breach of his fiduciary duties. The complaint also asserts an unjust enrichment claim against Mr. Plank. The complaint seeks damages on behalf of the Company and certain corporate governance-related actions. In King v. Plank, et al., filed on April 30, 2018, the complaint asserts similar breach of fiduciary duty claims against Mr. Plank and the director defendants and also claims that Sagamore aided and abetted the alleged breaches of fiduciary duty by the other defendants in connection with Sagamore’s alleged role in the sale of the parcels of land to the Company. The King complaint also asserts an unjust enrichment claim against Mr. Plank and Sagamore. It asserts similar damages to the damages sought in the Mioduszewski complaint. Prior to the filing of the Derivative Complaints, each of the purported stockholders had sent the Company a letter demanding that the Company pursue claims similar to the claims asserted in the Derivative Complaints. Following an investigation, a majority of disinterested and independent directors of the Company determined that the claims should not be pursued by the Company and informed each of these purported stockholders of that determination. The Company believes that the claims asserted in the Derivative Complaints are without merit and intends to defend these matters vigorously. However, because of the inherent uncertainty as to the outcome of these proceedings, the Company is unable at this time to estimate the possible impact of the outcome of these matters. Data Incident As previously disclosed, during the quarter ended March 31, 2018 an unauthorized third party acquired data associated with the Company’s Connected Fitness users’ accounts for the Company’s MyFitnessPal application and website. A consumer class action lawsuit has been filed against the Company in connection with this incident, and the Company has received inquiries regarding the incident from certain government regulators and agencies. The Company does not currently consider these matters to be material and believes its insurance coverage will provide coverage should any significant expense arise.

Commitments and Contingencies

There were no significant changes to the contractual obligations reported in the 2017 Form 10-K other than those which occur in the normal course of business.

In connection with various contracts and agreements, the Company has agreed to indemnify counterparties against certain third party claims relating to the infringement of intellectual property rights and other items. Generally, such indemnification obligations do not apply in situations in which the counterparties are grossly negligent, engage in willful misconduct, or act in bad faith. Based on the Company’s historical experience and the estimated probability of future loss, the Company has determined that the fair value of such indemnifications is not material to its consolidated financial position or results of operations.

From time to time, the Company is involved in litigation and other proceedings, including matters related to commercial and intellectual property disputes, as well as trade, regulatory and other claims related to its business. Other than as described below, the Company believes that all current proceedings are routine in nature and incidental to the conduct of its business, and that the ultimate resolution of any such proceedings will not have a material adverse effect on its consolidated financial position, results of operations or cash flows.

Securities Class Action

On March 23, 2017, three separate securities cases previously filed against the Company in the United States District Court for the District of Maryland (the “Court”) were consolidated under the caption In re Under Armour Securities Litigation, Case No. 17-cv-00388-RDB (the “Consolidated Action”). On August 4, 2017, the lead plaintiff in the Consolidated Action, North East Scotland Pension Fund, joined by named plaintiff Bucks County Employees Retirement Fund, filed a consolidated amended complaint (the “Amended Complaint”) against the Company, the Company’s Chief Executive Officer and former Chief Financial Officers, Lawrence Molloy and Brad Dickerson. The Amended Complaint alleges violations of Section 10(b) (and Rule 10b-5) of the Securities Exchange Act of 1934, as amended (the “Exchange Act”) and Section 20(a) control person liability under the Exchange Act against the officers named in the Amended Complaint, claiming that the defendants made material misstatements and omissions regarding, among other things, the Company's growth and consumer demand for certain of the Company's products. The class period identified in the Amended Complaint is September 16, 2015 through January 30, 2017. The Amended Complaint also asserts claims under Sections 11 and 15 of the Securities Act of 1933, as amended (the “Securities Act”), in connection with the Company’s public offering of senior unsecured notes in June 2016. The Securities Act claims are asserted against the Company, the Company’s Chief Executive Officer, Mr. Molloy, the Company’s directors who signed the registration statement pursuant to which the offering was made and the underwriters that participated in the offering. The Amended Complaint alleges that the offering materials utilized in connection with the offering contained false and/or misleading statements and omissions regarding, among other things, the Company’s growth and consumer demand for certain of the Company’s products. On November 9, 2017, the Company and the other defendants filed a motion to dismiss the Amended Complaint, which is still pending with the Court. The Company believes that the claims asserted in the Consolidated Action are without merit and intends to defend the lawsuit vigorously. However, because of the inherent uncertainty as to the outcome of this proceeding, the Company is unable at this time to estimate the possible impact of the outcome of this matter.

Derivative Complaints

In April 2018, two purported stockholders filed separate stockholder derivative complaints in the United States District Court for the District of Maryland (the “Derivative Complaints”). The Derivative Complaints were brought against Kevin Plank (the Company’s Chairman and Chief Executive Officer) and certain other members of the Company’s Board of Directors and name the Company as a nominal defendant. The Derivative Complaints make allegations related to the Company’s purchase of certain parcels of land from entities controlled by Mr. Plank (through Sagamore Development Company, LLC ("Sagamore")), as well as other alleged related party transactions.

Sagamore purchased these parcels in 2014. Its total investment in the parcels was approximately $72.0 million, which included the initial $35.0 million purchase price for the property, an additional $30.6 million to terminate a lease encumbering the property and approximately $6.4 million of development costs. As previously disclosed, in June 2016, the Company purchased the unencumbered parcels for $70.3 million in order to further expand the Company’s corporate headquarters to accommodate its growth needs. The Company negotiated a purchase price for the parcels that it determined represented the fair market value of the parcels and approximated the cost to the seller to purchase and develop the parcels. In connection with its evaluation of the potential purchase, the Company engaged an independent third-party to appraise the fair market value of the parcels, and the Audit Committee of the Company’s Board of Directors engaged its own independent appraisal firm to assess the parcels. The Audit Committee determined that the terms of the purchase were reasonable and fair, and the transaction was approved by the Audit Committee in accordance with the Company’s policy on transactions with related persons.

In Mioduszewski v. Plank, et al., filed on April 16, 2018, the complaint asserts that Mr. Plank and the director defendants breached their fiduciary duties in connection with the purchase of the parcels and other alleged related party transactions and that the director defendants aided and abetted Mr. Plank’s alleged breach of his fiduciary duties. The complaint also asserts an unjust enrichment claim against Mr. Plank. The complaint seeks damages on behalf of the Company and certain corporate governance-related actions. In King v. Plank, et al., filed on April 30, 2018, the complaint asserts similar breach of fiduciary duty claims against Mr. Plank and the director defendants and also claims that Sagamore aided and abetted the alleged breaches of fiduciary duty by the other defendants in connection with Sagamore’s alleged role in the sale of the parcels of land to the Company. The King complaint also asserts an unjust enrichment claim against Mr. Plank and Sagamore. It asserts similar damages to the damages sought in the Mioduszewski complaint.

Prior to the filing of the Derivative Complaints, each of the purported stockholders had sent the Company a letter demanding that the Company pursue claims similar to the claims asserted in the Derivative Complaints. Following an investigation, a majority of disinterested and independent directors of the Company determined that the claims should not be pursued by the Company and informed each of these purported stockholders of that determination. The Company believes that the claims asserted in the Derivative Complaints are without merit and intends to defend these matters vigorously. However, because of the inherent uncertainty as to the outcome of these proceedings, the Company is unable at this time to estimate the possible impact of the outcome of these matters.

Data Incident

As previously disclosed, during the quarter ended March 31, 2018 an unauthorized third party acquired data associated with the Company’s Connected Fitness users’ accounts for the Company’s MyFitnessPal application and website. A consumer class action lawsuit has been filed against the Company in connection with this incident, and the Company has received inquiries regarding the incident from certain government regulators and agencies. The Company does not currently consider these matters to be material and believes its insurance coverage will provide coverage should any significant expense arise.