Subsequent Events	12 Months Ended
Dec. 31, 2017
Subsequent Events [Abstract]
Subsequent Events	21. Subsequent Events Private Exchange of Convertible Notes. On February 12, 2018, the Company entered into the Exchange Agreements. On February 22, 2018, the Company consummated the Note Exchange, pursuant to which the Company exchanged approximately $125 million aggregate principal amount of 1.50% Convertible Notes for 5.75% Convertible Notes issued by the Company in an aggregate principal amount of approximately $125 million. Consummation of the Note Exchange satisfied one of the principal conditions to the availability of the Second Delayed Draw Term Loan under the DB Credit Agreement that the Company achieve a reduction in the outstanding principal amount of the 1.50% Convertible Notes of at least $100.0 million. In addition, the Company satisfied the remaining conditions to the availability of the Second Delayed Draw Term Loan, which included (i) the Company being in financial covenant compliance, on a pro forma basis as of the time of the requested borrowing and on a projected basis for the succeeding 12 months based on projections reasonably acceptable to the lenders, and (ii) there not existing a default or event of default under the DB Credit Agreement as of the time of the borrowing. On March 14, 2018, the Company drew down $110 million under the Second Delayed Draw Term Loan and used those proceeds, along with cash on hand, to make a payment to the trustee under the indenture governing the 1.50% Convertible Notes in an amount to repay the remaining 1.50% Convertible Notes at maturity on March 15, 2018. Interest on the 5.75% Convertible Notes may be paid in cash, shares of the Company’s common stock, or a combination of both, at the Company’s election, subject to the Aggregate Share Cap (as described below). If the Company elects to pay all or a portion of an interest payment in shares of common stock, the number of shares of common stock payable will be equal to the applicable interest payment divided by the average of the 10 individual volume-weighted average prices for the 10-trading day period ending on and including the trading day immediately preceding the relevant interest payment date. The 5.75% Convertible Notes are (i) secured by a second lien on the same assets that secure the obligations of IBG Borrower under the DB Credit Agreement and (ii) guaranteed by IBG Borrower and same guarantors as those under the DB Credit Agreement, other than the Company. Unless and until the Company obtains requisite stockholder approval to increase the Aggregate Share Cap, the aggregate number of shares of common stock deliverable by the Company will be subject to the Aggregate Share Cap. The Company will not be obligated to make payments in cash in lieu of shares of common stock until April 15, 2019. Subject to certain conditions and limitations, the Company may cause all or part of the 5.75% Convertible Notes to be automatically converted. Holders converting their 5.75% Convertible Notes (including in connection with a mandatory conversion) shall also be entitled to receive a payment from the Company equal to the Conversion Make-Whole Payment if such conversion occurs after a regular record date and on or before the next succeeding interest payment date), through and including the maturity date (determined as if such conversion did not occur). If the Company elects to pay all or a portion of a Conversion Make-Whole Payment in shares of common stock, the number of shares of common stock payable will be equal to the applicable Conversion Make-Whole Payment divided by the average of the 10 individual volume-weighted average prices for the 10-trading day period immediately preceding the applicable conversion date. Subject to certain limitations pursuant to the DB Credit Agreement, from and after the one-year anniversary of the closing of the Note Exchange, the Company may redeem for cash all or part of the 5.75% Convertible Notes at any time by providing at least 30 days’ prior written notice to holders of the 5.75% Convertible Notes. If the Company undergoes a fundamental change prior to maturity, each holder will have the right, at its option, to require the Company to repurchase for cash all or a portion of such holder’s 5.75% Convertible Notes at a fundamental change purchase price equal to 100% of the principal amount of the 5.75% Convertible Notes to be repurchased, together with interest accrued and unpaid to, but excluding, the fundamental change purchase date. The Company will be subject to certain restrictive covenants pursuant to the 5.75% Convertible Note Indenture, including limitations on (i) liens, (ii) indebtedness, (iii) asset sales, (iv) restricted payments and investments, (v) prepayments of indebtedness and (vi) transactions with affiliates. Third Amendment to the DB Credit Agreement. On February 12, 2018, the Company, through IBG Borrower, entered the Third Amendment to the DB Credit Agreement. The Third Amendment provides for, among other things, amendments to certain restrictive covenants and other terms set forth in the DB Credit Agreement, as amended, to permit (i) IBG Borrower to enter into the 5.75% Notes Indenture (as described above) and a related intercreditor agreement that is anticipated to be executed and (ii) the Note Exchange. In connection with the Third Amendment, Deutsche Bank was granted additional pricing flex in the form of price protection upon syndication of the loan (“Third Amendment Flex”). After giving effect to the additional Third Amendment Flex, the Company estimates that it could be responsible for payments on account of the Third Amendment Flex in an aggregate total amount of up to $6.1 million. Fourth Amendment to the DB Credit Agreement. The Company, through IBG Borrower, entered into the Fourth Amendment to the DB Credit Agreement as of March 12, 2018. The Fourth Amendment provides, among other things, that the funding date for the Second Delayed Draw Term Loan is March 14, 2018 instead of March 15, 2018. Repayment of Remaining 1.50% Convertible Notes. On March 14, 2018, the Company drew down $110 million under the Second Delayed Draw Term Loan and used those proceeds, along with cash on hand, to make a payment to the trustee under the indenture governing the 1.50% Convertible Notes to repay the remaining 1.50% Convertible Notes at maturity on March 15, 2018. Complex Media. On January 30, 2018, the Company received the remaining escrow balance of approximately $1.0 million in relation to the sale of the Company’s ownership interest in Complex Media. Refer to Note 4 for further details.

21. Subsequent Events

Private Exchange of Convertible Notes. On February 12, 2018, the Company entered into the Exchange Agreements. On February 22, 2018, the Company consummated the Note Exchange, pursuant to which the Company exchanged approximately $125 million aggregate principal amount of 1.50% Convertible Notes for 5.75% Convertible Notes issued by the Company in an aggregate principal amount of approximately $125 million.

Consummation of the Note Exchange satisfied one of the principal conditions to the availability of the Second Delayed Draw Term Loan under the DB Credit Agreement that the Company achieve a reduction in the outstanding principal amount of the 1.50% Convertible Notes of at least $100.0 million. In addition, the Company satisfied the remaining conditions to the availability of the Second Delayed Draw Term Loan, which included (i) the Company being in financial covenant compliance, on a pro forma basis as of the time of the requested borrowing and on a projected basis for the succeeding 12 months based on projections reasonably acceptable to the lenders, and (ii) there not existing a default or event of default under the DB Credit Agreement as of the time of the borrowing. On March 14, 2018, the Company drew down $110 million under the Second Delayed Draw Term Loan and used those proceeds, along with cash on hand, to make a payment to the trustee under the indenture governing the 1.50% Convertible Notes in an amount to repay the remaining 1.50% Convertible Notes at maturity on March 15, 2018.

Interest on the 5.75% Convertible Notes may be paid in cash, shares of the Company’s common stock, or a combination of both, at the Company’s election, subject to the Aggregate Share Cap (as described below). If the Company elects to pay all or a portion of an interest payment in shares of common stock, the number of shares of common stock payable will be equal to the applicable interest payment divided by the average of the 10 individual volume-weighted average prices for the 10-trading day period ending on and including the trading day immediately preceding the relevant interest payment date.

The 5.75% Convertible Notes are (i) secured by a second lien on the same assets that secure the obligations of IBG Borrower under the DB Credit Agreement and (ii) guaranteed by IBG Borrower and same guarantors as those under the DB Credit Agreement, other than the Company.

Unless and until the Company obtains requisite stockholder approval to increase the Aggregate Share Cap, the aggregate number of shares of common stock deliverable by the Company will be subject to the Aggregate Share Cap.

The Company will not be obligated to make payments in cash in lieu of shares of common stock until April 15, 2019.

Subject to certain conditions and limitations, the Company may cause all or part of the 5.75% Convertible Notes to be automatically converted.

Holders converting their 5.75% Convertible Notes (including in connection with a mandatory conversion) shall also be entitled to receive a payment from the Company equal to the Conversion Make-Whole Payment if such conversion occurs after a regular record date and on or before the next succeeding interest payment date), through and including the maturity date (determined as if such conversion did not occur).

If the Company elects to pay all or a portion of a Conversion Make-Whole Payment in shares of common stock, the number of shares of common stock payable will be equal to the applicable Conversion Make-Whole Payment divided by the average of the 10 individual volume-weighted average prices for the 10-trading day period immediately preceding the applicable conversion date.

Subject to certain limitations pursuant to the DB Credit Agreement, from and after the one-year anniversary of the closing of the Note Exchange, the Company may redeem for cash all or part of the 5.75% Convertible Notes at any time by providing at least 30 days’ prior written notice to holders of the 5.75% Convertible Notes.

If the Company undergoes a fundamental change prior to maturity, each holder will have the right, at its option, to require the Company to repurchase for cash all or a portion of such holder’s 5.75% Convertible Notes at a fundamental change purchase price equal to 100% of the principal amount of the 5.75% Convertible Notes to be repurchased, together with interest accrued and unpaid to, but excluding, the fundamental change purchase date.

The Company will be subject to certain restrictive covenants pursuant to the 5.75% Convertible Note Indenture, including limitations on (i) liens, (ii) indebtedness, (iii) asset sales, (iv) restricted payments and investments, (v) prepayments of indebtedness and (vi) transactions with affiliates.

Third Amendment to the DB Credit Agreement. On February 12, 2018, the Company, through IBG Borrower, entered the Third Amendment to the DB Credit Agreement. The Third Amendment provides for, among other things, amendments to certain restrictive covenants and other terms set forth in the DB Credit Agreement, as amended, to permit (i) IBG Borrower to enter into the 5.75% Notes Indenture (as described above) and a related intercreditor agreement that is anticipated to be executed and (ii) the Note Exchange. In connection with the Third Amendment, Deutsche Bank was granted additional pricing flex in the form of price protection upon syndication of the loan (“Third Amendment Flex”). After giving effect to the additional Third Amendment Flex, the Company estimates that it could be responsible for payments on account of the Third Amendment Flex in an aggregate total amount of up to $6.1 million.

Fourth Amendment to the DB Credit Agreement. The Company, through IBG Borrower, entered into the Fourth Amendment to the DB Credit Agreement as of March 12, 2018. The Fourth Amendment provides, among other things, that the funding date for the Second Delayed Draw Term Loan is March 14, 2018 instead of March 15, 2018.

Repayment of Remaining 1.50% Convertible Notes. On March 14, 2018, the Company drew down $110 million under the Second Delayed Draw Term Loan and used those proceeds, along with cash on hand, to make a payment to the trustee under the indenture governing the 1.50% Convertible Notes to repay the remaining 1.50% Convertible Notes at maturity on March 15, 2018.

Complex Media. On January 30, 2018, the Company received the remaining escrow balance of approximately $1.0 million in relation to the sale of the Company’s ownership interest in Complex Media. Refer to Note 4 for further details.