Joint Venture (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017	Oct. 01, 2018	Dec. 31, 2016
Schedule of Equity Method Investments [Line Items]
Deferred income tax assets			$ 181,783	$ 166,762
Equity interest in earnings (losses) of joint venture			12,932	3,339	$ 2,568
Costs recognized to fulfill a contract			105,206
ASC 606 [Member]
Schedule of Equity Method Investments [Line Items]
Revenue recognized to contract liabilities						$ 57,529
Costs recognized to fulfill a contract						$ 57,529
Additional contract liabilities			14,340
Additional costs to fulfill a contract			14,324
Reduction in contract assets and costs to fulfill contract			2,774
Reduction in contract liabilities and costs to fulfill contract			$ 2,790
Woodward and General Electric Joint Venture [Member]
Schedule of Equity Method Investments [Line Items]
Agreement to Form Joint Venture, Execution Date			Jan. 04, 2016
Ownership interest, joint venture			50.00%				50.00%
Cash received from formation of joint venture			$ 250,000
Cash received annually from formation of joint venture	$ 4,894	$ 4,894	4,894
Current portion of deferred income recorded in connection with joint venture			8,317	7,087
Noncurrent portion of deferred income recorded in connection with joint venture			230,588	235,300
Equity interest in earnings (losses) of joint venture			12,932	3,339	2,568
Cash distributions from joint venture			15,000	0	2,500
Net investment in joint venture			7,543	9,611
Accounts receivable from related party			5,906	10,499
Accounts payable to related party			4,270	2,944
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			7,652	5,854	6,286
Sales to related party			60,955	72,511	70,234
Reduction to sales related to royalties paid to joint venture			$ 34,236	$ 26,023	$ 26,133