Business Combination

9 Months Ended

Sep. 30, 2014

Business Combination [Abstract]

Merger Transaction Agreement

(2)  Merger Transaction Agreement

On April 28, 2014, Orbital entered into a definitive transaction agreement (the "Transaction Agreement") with Alliant Techsystems Inc. ("ATK") that provides for the merger (the "Merger") of Orbital with the Aerospace and Defense Groups of ATK ("ATK A&D") following the spin-off of ATK's Sporting Group business ("Sporting") to ATK's stockholders (the "Distribution" and together with the Merger, the "Transaction").  At closing, the combined company will be named Orbital ATK, Inc. ("Orbital ATK").  The Transaction Agreement provides that each share of Orbital's common stock issued and outstanding immediately prior to the Merger will be converted into the right to receive 0.449 shares of ATK common stock.  Orbital's stockholders will own approximately 46.2% of Orbital ATK, and ATK's stockholders will own approximately 53.8% of Orbital ATK at the closing of the Transaction.  This transaction is subject to stockholder approval and other customary closing conditions.