Transition Period Comparative Data (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								6 Months Ended	9 Months Ended			12 Months Ended				18 Months Ended	21 Months Ended
	Dec. 31, 2015	Oct. 04, 2015	Jul. 05, 2015	Jul. 04, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 28, 2014	Jun. 29, 2014	Oct. 04, 2015	Dec. 31, 2015	[1]	Dec. 28, 2014	Mar. 31, 2015	[1]	Mar. 31, 2014	[1]	Sep. 28, 2014	Dec. 31, 2014
Quarterly Financial Information Disclosure [Abstract]
Revenues	$ 1,144,560	$ 1,143,246	$ 1,103,578		$ 971,150	$ 724,541	$ 722,012	$ 694,956	$ 2,246,823	$ 3,391,384		$ 2,141,509	$ 3,112,659		$ 2,890,711		$ 1,416,968	$ 2,141,509
Gross profit	242,470	208,817	222,861		223,273	161,196	158,195	158,239	431,678	674,148		477,630	700,903		290,104		316,434	477,630
Income from continuing operations of Orbital ATK, Inc.	53,296	74,047	57,836		(39,353)	42,373	37,894	28,937	131,883	185,179		109,205	69,851		(64,429)		66,831	109,205
Income from discontinued operations	1,008	0	0	$ 0	16,837	492	53,895	53,825	0	1,008		108,210	125,049		181,463		107,720	108,210
Net income attributable to Orbital ATK, Inc.	$ 54,304	$ 74,047	$ 57,836		$ (22,516)	$ 42,865	$ 91,789	$ 82,762	$ 131,883	$ 186,187		$ 217,415	$ 194,900		$ 117,034		$ 174,551	$ 217,415
Continuing operations (in dollars per share)	$ 0.90	$ 1.26	$ 0.98		$ (0.84)	$ 1.33	$ 1.20	$ 0.91	$ 2.24	$ 3.12		$ 3.44	$ 1.96		$ (2.03)		$ 2.11	$ 3.44
Discontinued operations (in dollars per share)	0.02	0.00	0.00		0.36	0.02	1.70	1.70	0.00	0.02		3.42	3.53		5.73		3.40	3.42
Basic (in dollars per share)	0.92	1.26	0.98		(0.48)	1.35	2.90	2.61	2.24	3.14		6.86	5.49		3.70		5.51	6.86
Continuing operations (in dollars per share)	0.89	1.25	0.97		(0.84)	1.32	1.18	0.87	2.22	3.09		3.37	1.93		(1.97)		2.05	3.37
Discontinued operations (in dollars per share)	0.02	0.00	0.00		0.36	0.02	1.68	1.63	0.00	0.02		3.34	3.46		5.55		3.30	3.34
Diluted (in dollars per share)	$ 0.91	$ 1.25	$ 0.97		$ (0.48)	$ 1.34	$ 2.86	$ 2.50	$ 2.22	$ 3.11		$ 6.71	$ 5.39		$ 3.58		$ 5.35	$ 6.71

[1] See Note 2 - Restatement