Joint Ventures (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2018	Mar. 31, 2017	Sep. 30, 2016	Sep. 30, 2017	Jan. 04, 2016
Schedule of Equity Method Investments [Line Items]
Current portion of deferred income recorded in connection with joint venture	$ 6,427		$ 6,427			$ 6,451
Noncurrent portion of deferred income recorded in connection with joint venture	239,275		239,275			236,896
Equity interest in earnings (losses) of joint venture	$ 1,006	$ 382	$ 1,602	$ 1,066
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%		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	6,427		$ 6,427			6,451
Noncurrent portion of deferred income recorded in connection with joint venture	239,275		239,275			236,896
Equity interest in earnings (losses) of joint venture	1,006	382	1,602	1,066
Cash distributions from joint venture			0	2,500
Net investment in joint venture	7,874		7,874			6,272
Accounts receivable from related party	9,755		9,755			8,554
Accounts payable to related party	6,420		6,420			$ 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	1,486	1,632	2,539	3,128
Sales to related party	17,077	18,415	30,052	33,717
Reduction to sales related to royalties paid to joint venture	6,922	$ 5,674	$ 12,330	$ 11,077
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