Merger With GETCO and formation of KCG Holdings Inc.	6 Months Ended
Jun. 30, 2013
Business Combinations [Abstract]
Merger With GETCO and formation of KCG Holdings Inc.	Merger with GETCO and Formation of KCG Holdings, Inc. Background On December 19, 2012, Knight, GETCO Holding Company, LLC (“GETCO”) and an affiliate of GETCO entered into an agreement and plan of merger (as amended and restated on April 15, 2013) (the “Merger Agreement”) for a series of strategic business combinations (the “Mergers”). The Mergers were approved by the respective shareholders and unitholders of both companies at special meetings held on June 25, 2013, and the Mergers were completed on July 1, 2013. As a result of the Mergers, Knight and GETCO each became a wholly-owned subsidiary of KCG Holdings, Inc. (“KCG”). Pursuant to the Merger Agreement, upon completion of the Knight Merger, subject to proration and certain specified exceptions, each outstanding share of Knight Class A common stock, par value $0.01 per share (“Knight Common Stock”) was converted into the right to elect to receive either $3.75 per share in cash or one third of a share of KCG Class A common stock, par value $0.01 per share (“KCG Class A Common Stock”). Pursuant to the proration procedures provided in the Merger Agreement and taking into account the waiver by Jefferies LLC, Knight's largest shareholder before the Knight Merger, of its right to receive cash consideration with respect to certain of its shares, former Knight shareholders eligible for election received a cash payment of approximately $720.0 million. Upon completion of the Mergers, GETCO unitholders received, in aggregate, 75.9 million shares of KCG Class A Common Stock and 24.3 million warrants to acquire shares of KCG Class A Common Stock. The warrants comprise 8.1 million Class A warrants, having a $12.00 exercise price and exercisable for a four-year term; 8.1 million Class B warrants, having a $13.50 exercise price and exercisable for a five-year term; and 8.1 million Class C warrants, having a $15.00 exercise price and exercisable for a six-year term (collectively the “KCG Warrants”). As of June 30, 2013 there were 373.3 million shares of Knight Common Stock outstanding. On July 1, 2013, KCG paid $720.0 million in cash consideration to former Knight stockholders (excluding cash to be paid in lieu of fractional shares of KCG Class A Common Stock) in exchange for 192.0 million shares of Knight Common Stock. After taking into account the election results, the effect of a 3:1 stock conversion and the shares of KCG Class A Common Stock issued to former unitholders of GETCO, 116.8 million shares (including unvested restricted stock units ("RSUs")) of KCG Class A Common Stock were outstanding as of July 1, 2013. Accounting treatment of the Mergers The Mergers are accounted for as a purchase of Knight by GETCO under accounting principles generally accepted in the United States of America ("GAAP"). Under the purchase method of accounting, the assets and liabilities of Knight will be recorded, as of completion of the Mergers, at their respective fair values and added to the carrying value of GETCO's existing assets and liabilities. The reported financial condition and results of operations of KCG following completion of the Mergers will reflect Knight's and GETCO's balances and will reflect the impact of purchase accounting adjustments, including revised amortization and depreciation expense for acquired assets. As GETCO is the accounting acquirer, all historical financial information will be of legacy GETCO. The Company recorded certain expenses in the second quarter of 2013 because the Mergers were substantially completed as of the close of business on June 30, 2013. These expenses primarily included success-based professional fees and accelerated stock-based compensation. The stock-based compensation was accelerated as a result of the change-in-control provisions of equity-based awards issued prior to December 19, 2012 that were triggered by the Mergers.

Merger with GETCO and Formation of KCG Holdings, Inc.

Background

On December 19, 2012, Knight, GETCO Holding Company, LLC (“GETCO”) and an affiliate of GETCO entered into an agreement and plan of merger (as amended and restated on April 15, 2013) (the “Merger Agreement”) for a series of strategic business combinations (the “Mergers”). The Mergers were approved by the respective shareholders and unitholders of both companies at special meetings held on June 25, 2013, and the Mergers were completed on July 1, 2013. As a result of the Mergers, Knight and GETCO each became a wholly-owned subsidiary of KCG Holdings, Inc. (“KCG”).

Pursuant to the Merger Agreement, upon completion of the Knight Merger, subject to proration and certain specified exceptions, each outstanding share of Knight Class A common stock, par value $0.01 per share (“Knight Common Stock”) was converted into the right to elect to receive either $3.75 per share in cash or one third of a share of KCG Class A common stock, par value $0.01 per share (“KCG Class A Common Stock”). Pursuant to the proration procedures provided in the Merger Agreement and taking into account the waiver by Jefferies LLC, Knight's largest shareholder before the Knight Merger, of its right to receive cash consideration with respect to certain of its shares, former Knight shareholders eligible for election received a cash payment of approximately $720.0 million.

Upon completion of the Mergers, GETCO unitholders received, in aggregate, 75.9 million shares of KCG Class A Common Stock and 24.3 million warrants to acquire shares of KCG Class A Common Stock. The warrants comprise 8.1 million Class A warrants, having a $12.00 exercise price and exercisable for a four-year term; 8.1 million Class B warrants, having a $13.50 exercise price and exercisable for a five-year term; and 8.1 million Class C warrants, having a $15.00 exercise price and exercisable for a six-year term (collectively the “KCG Warrants”).

As of June 30, 2013 there were 373.3 million shares of Knight Common Stock outstanding. On July 1, 2013, KCG paid $720.0 million in cash consideration to former Knight stockholders (excluding cash to be paid in lieu of fractional shares of KCG Class A Common Stock) in exchange for 192.0 million shares of Knight Common Stock. After taking into account the election results, the effect of a 3:1 stock conversion and the shares of KCG Class A Common Stock issued to former unitholders of GETCO, 116.8 million shares (including unvested restricted stock units ("RSUs")) of KCG Class A Common Stock were outstanding as of July 1, 2013.

Accounting treatment of the Mergers

The Mergers are accounted for as a purchase of Knight by GETCO under accounting principles generally accepted in the United States of America ("GAAP"). Under the purchase method of accounting, the assets and liabilities of Knight will be recorded, as of completion of the Mergers, at their respective fair values and added to the carrying value of GETCO's existing assets and liabilities. The reported financial condition and results of operations of KCG following completion of the Mergers will reflect Knight's and GETCO's balances and will reflect the impact of purchase accounting adjustments, including revised amortization and depreciation expense for acquired assets. As GETCO is the accounting acquirer, all historical financial information will be of legacy GETCO.

The Company recorded certain expenses in the second quarter of 2013 because the Mergers were substantially completed as of the close of business on June 30, 2013. These expenses primarily included success-based professional fees and accelerated stock-based compensation. The stock-based compensation was accelerated as a result of the change-in-control provisions of equity-based awards issued prior to December 19, 2012 that were triggered by the Mergers.