Joint Ventures (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
	Mar. 31, 2018	Sep. 30, 2016	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016	Jan. 04, 2016
Schedule of Equity Method Investments [Line Items]
Cash received from formation of joint venture					$ 250,000
Current portion of deferred income recorded in connection with joint venture			$ 7,087	$ 6,451
Noncurrent portion of deferred income recorded in connection with joint venture			235,300	236,896
Deferred income tax assets			166,762	201,970
Equity interest in earnings (losses) of joint venture			$ 3,339	2,568	$ 6,204
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	$ 4,894				$ 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			7,087	6,451
Noncurrent portion of deferred income recorded in connection with joint venture			235,300	236,896
Equity interest in earnings (losses) of joint venture		$ 6,204	3,339	2,568
Cash distributions from joint venture			0	2,500
Net investment in joint venture			9,611	6,272
Accounts receivable from related party			10,499	8,554
Accounts payable to related party			2,944	6,741
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		5,261	5,854	6,286
Sales to related party		46,973	72,511	70,234
Reduction to sales related to royalties paid to joint venture		$ 21,391	$ 26,023	$ 26,133
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