Business Description and Basis of Presentation	3 Months Ended
Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Business Description and Basis of Presentation	Business Description and Basis of Presentation Rockwell Collins, Inc. (the Company or Rockwell Collins) designs, produces and supports cabin interior, communications and aviation systems and products for commercial and military customers and provides information management services through voice and data communication networks and solutions worldwide. The Company operates on a 52/53 week fiscal year with quarters ending on the Friday closest to the last day of the calendar quarter. For ease of presentation, December 31 and September 30 are utilized consistently throughout these financial statements and notes to represent the period end dates. The Company has two consolidated subsidiaries with income attributable to a noncontrolling interest. The net income and comprehensive income attributable to the noncontrolling interest is insignificant. The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America and with the instructions to Form 10-Q of the Securities and Exchange Commission. Certain information and footnote disclosures normally included in annual financial statements have been condensed or omitted. These financial statements should be read in conjunction with the Company's Annual Report on Form 10-K for the year ended September 30, 2017. In the opinion of management, the unaudited financial statements contain all adjustments, consisting of adjustments of a normal recurring nature, necessary to present fairly the financial position, results of operations and cash flows for the periods presented. The results of operations for the three months ended December 31, 2017 are not necessarily indicative of the results that may be expected for the full year. The preparation of financial statements in accordance with accounting principles generally accepted in the United States of America requires management to make estimates and assumptions that affect the amounts reported in the financial statements. Actual results could differ from those estimates and assumptions. On September 4, 2017, the Company entered into an Agreement and Plan of Merger (Merger Agreement) with United Technologies Corporation (UTC). The Merger Agreement provides that the Company will be acquired by UTC. Each Company shareowner will receive $93.33 per share in cash and $46.67 in shares of UTC common stock in the merger, subject to a 7.5 percent collar centered on UTC's August 22, 2017 closing share price of $115.69. The transaction, which is expected to close by the third calendar quarter of 2018, is subject to the satisfaction of customary closing conditions and approval by certain regulators. The Company incurred $10 million of merger-related costs during the three months ended December 31, 2017. These costs are included in Transaction and integration costs in the Condensed Consolidated Statement of Operations. At December 31, 2017, $18 million of merger-related costs, including amounts expensed in fiscal year 2017, were unpaid and included in Accounts payable and Compensation and benefits on the Condensed Consolidated Statement of Financial Position. On April 13, 2017, the Company acquired B/E Aerospace, a leading manufacturer of aircraft cabin interior products and services. Prior to 2018, the financial results of the entire B/E Aerospace business were reported in a new Interior Systems segment. Beginning in 2018, the B/E Aerospace thermal and electronic systems product lines, which primarily serve military and government customers, are now being reported in the Government Systems segment. This reorganization is expected to generate additional revenue synergy opportunities for the Company. The results of operations of the acquired B/E Aerospace business are now reported in the Interior Systems and Government Systems business segments.

Business Description and Basis of Presentation

Rockwell Collins, Inc. (the Company or Rockwell Collins) designs, produces and supports cabin interior, communications and aviation systems and products for commercial and military customers and provides information management services through voice and data communication networks and solutions worldwide.

The Company operates on a 52/53 week fiscal year with quarters ending on the Friday closest to the last day of the calendar quarter. For ease of presentation, December 31 and September 30 are utilized consistently throughout these financial statements and notes to represent the period end dates.

The Company has two consolidated subsidiaries with income attributable to a noncontrolling interest. The net income and comprehensive income attributable to the noncontrolling interest is insignificant.

The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America and with the instructions to Form 10-Q of the Securities and Exchange Commission. Certain information and footnote disclosures normally included in annual financial statements have been condensed or omitted. These financial statements should be read in conjunction with the Company's Annual Report on Form 10-K for the year ended September 30, 2017.

In the opinion of management, the unaudited financial statements contain all adjustments, consisting of adjustments of a normal recurring nature, necessary to present fairly the financial position, results of operations and cash flows for the periods presented. The results of operations for the three months ended December 31, 2017 are not necessarily indicative of the results that may be expected for the full year.

The preparation of financial statements in accordance with accounting principles generally accepted in the United States of America requires management to make estimates and assumptions that affect the amounts reported in the financial statements. Actual results could differ from those estimates and assumptions.

On September 4, 2017, the Company entered into an Agreement and Plan of Merger (Merger Agreement) with United Technologies Corporation (UTC). The Merger Agreement provides that the Company will be acquired by UTC. Each Company shareowner will receive $93.33 per share in cash and $46.67 in shares of UTC common stock in the merger, subject to a 7.5 percent collar centered on UTC's August 22, 2017 closing share price of $115.69. The transaction, which is expected to close by the third calendar quarter of 2018, is subject to the satisfaction of customary closing conditions and approval by certain regulators. The Company incurred $10 million of merger-related costs during the three months ended December 31, 2017. These costs are included in Transaction and integration costs in the Condensed Consolidated Statement of Operations. At December 31, 2017, $18 million of merger-related costs, including amounts expensed in fiscal year 2017, were unpaid and included in Accounts payable and Compensation and benefits on the Condensed Consolidated Statement of Financial Position.

On April 13, 2017, the Company acquired B/E Aerospace, a leading manufacturer of aircraft cabin interior products and services. Prior to 2018, the financial results of the entire B/E Aerospace business were reported in a new Interior Systems segment. Beginning in 2018, the B/E Aerospace thermal and electronic systems product lines, which primarily serve military and government customers, are now being reported in the Government Systems segment. This reorganization is expected to generate additional revenue synergy opportunities for the Company. The results of operations of the acquired B/E Aerospace business are now reported in the Interior Systems and Government Systems business segments.