Joint Ventures (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015	Jan. 04, 2016
Schedule of Equity Method Investments [Line Items]
Cash received from formation of joint venture			$ 0	$ 250,000	$ 0
Current portion of deferred income recorded in connection with joint venture			6,451	6,552
Noncurrent portion of deferred income recorded in connection with joint venture			236,896	238,187
Deferred income tax assets			201,970	206,966
Equity interest in earnings (losses) of joint venture			$ 2,568	$ 6,204	$ 0
Woodward and General Electric Joint Venture [Member]
Schedule of Equity Method Investments [Line Items]
Agreement to Form Joint Venture, Execution Date				Jan. 04, 2016
Equity Method Investment, Ownership Percentage			50.00%
Cash received from formation of joint venture		$ 250,000
Cash received annually from formation of joint venture	$ 4,894
Amount of deferred income recorded in connection with joint venture						$ 250,000
Current portion of deferred income recorded in connection with joint venture			$ 6,451	$ 6,552
Noncurrent portion of deferred income recorded in connection with joint venture			236,896	238,187
Equity interest in earnings (losses) of joint venture			2,568	6,204
Cash distributions from joint venture			2,500	0
Net investment in joint venture			6,272	6,204
Accounts receivable from related party			8,554	5,326
Accounts payable to related party			6,741	3,926
Woodward and General Electric Joint Venture [Member] | Sales [Member]
Schedule of Equity Method Investments [Line Items]
Amortization of deferred income recognized as an increase to sales			6,286	5,261
Sales to related party			70,234	46,973
Reduction to sales related to royalties paid to joint venture			26,133	$ 21,391
Woodward and General Electric Joint Venture [Member] | Scenario, Forecast [Member]
Schedule of Equity Method Investments [Line Items]
Cash received annually from formation of joint venture			$ 4,894