Segment Information (U.S. Government Related Sales by Segment) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Revenue, Major Customer [Line Items]
Net sales	$ 606,788	$ 548,622	$ 500,381	$ 442,894	$ 590,922	$ 507,664	$ 479,382	$ 445,110	$ 2,098,685	$ 2,023,078	$ 2,038,303
Aerospace [Member]
Revenue, Major Customer [Line Items]
Net sales	399,141	355,992	320,526	266,680	365,305	308,582	290,690	268,599	1,342,339	1,233,176	1,160,883
Industrial [Member]
Revenue, Major Customer [Line Items]
Net sales	$ 207,647	$ 192,630	$ 179,855	$ 176,214	$ 225,617	$ 199,082	$ 188,692	$ 176,511	756,346	789,902	877,420
U.S. Government Related [Member]
Revenue, Major Customer [Line Items]
Net sales									$ 483,761	$ 430,373	$ 364,388
Percentage of total attributable to major customer									23.00%	21.00%	18.00%
U.S. Government Related [Member] | Aerospace [Member]
Revenue, Major Customer [Line Items]
Net sales									$ 469,221	$ 413,978	$ 350,713
U.S. Government Related [Member] | Industrial [Member]
Revenue, Major Customer [Line Items]
Net sales									14,540	16,395	13,675
Indirect Sales to U.S. Government [Member]
Revenue, Major Customer [Line Items]
Net sales									$ 373,350	$ 320,797	$ 267,230
Percentage of total attributable to major customer									18.00%	16.00%	13.00%
Indirect Sales to U.S. Government [Member] | Aerospace [Member]
Revenue, Major Customer [Line Items]
Net sales									$ 362,536	$ 310,952	$ 258,391
Indirect Sales to U.S. Government [Member] | Industrial [Member]
Revenue, Major Customer [Line Items]
Net sales									10,814	9,845	8,839
Direct Sales to U.S. Government [Member]
Revenue, Major Customer [Line Items]
Net sales									$ 110,411	$ 109,576	$ 97,158
Percentage of total attributable to major customer									5.00%	5.00%	5.00%
Direct Sales to U.S. Government [Member] | Aerospace [Member]
Revenue, Major Customer [Line Items]
Net sales									$ 106,685	$ 103,026	$ 92,322
Direct Sales to U.S. Government [Member] | Industrial [Member]
Revenue, Major Customer [Line Items]
Net sales									$ 3,726	$ 6,550	$ 4,836
Sales [Member] | General Electric [Member]
Revenue, Major Customer [Line Items]
Percentage of total attributable to major customer									16.00%	17.00%	18.00%
Trade Accounts Receivable [Member] | U.S. Government Related [Member]
Revenue, Major Customer [Line Items]
Percentage of total attributable to major customer									3.00%	2.00%
Trade Accounts Receivable [Member] | General Electric [Member]
Revenue, Major Customer [Line Items]
Percentage of total attributable to major customer									10.00%	14.00%