Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended								6 Months Ended	9 Months Ended	12 Months Ended
	Dec. 31, 2020	Sep. 27, 2020	Jun. 28, 2020	Mar. 29, 2020	Dec. 31, 2019	Sep. 29, 2019	Jun. 30, 2019	Mar. 31, 2019	Jun. 28, 2020	Sep. 27, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Statement [Abstract]
Revenues	$ 787,833	$ 666,240	$ 643,303	$ 617,253	$ 697,085	$ 697,717	$ 695,607	$ 673,484	$ 1,260,556	$ 1,926,795	$ 2,714,628	$ 2,763,893	$ 2,608,562
Cost of revenues	623,390	512,877	496,678	465,208	559,940	565,703	540,772	517,159	961,886	1,474,763	2,098,153	2,183,574	1,991,622
Selling, general and administrative expenses		119,168	105,451	137,326					242,777	361,945	498,827	530,080	536,019
Amortization of intangible assets		8,047	8,047	8,047					16,094	24,141	34,154	33,205	35,780
Total operating expenses		640,092	610,176	610,581					1,220,757	1,860,849	2,631,134	2,746,859	2,563,421
Program profit		26,148	33,127	6,672					39,799	65,946	83,494	17,034	45,141
Other operating income, net		2,384	1,168	785					1,954	4,338	7,272	9,785	4,980
Operating income	$ 20,482	28,532	34,295	7,457	(3,167)	(10,525)	26,158	14,353	41,753	70,284	90,766	26,819	50,121
Interest expense, net		(13,607)	(13,757)	(20,948)					(34,705)	(48,312)	(73,857)	(86,011)	(84,360)
Other income, net		5,000	(19,467)	30,112					10,645	15,645	12,645	0	0
Income (loss) before income taxes		19,925	1,071	16,621					17,693	37,617	29,554	(59,192)	(34,239)
Expense (benefit) from income taxes		4,194	3,752	(9,529)					(5,776)	(1,582)	2,268	(9,131)	(2,661)
Net income (loss)		15,731	(2,681)	26,150	$ (16,664)	$ (31,625)	$ 3,388	$ (5,160)	23,469	39,199	27,286	(50,061)	(31,578)
Noncontrolling interest in earnings of ventures		413	765	166					931	1,344	(1,464)	(252)	2,881
Net income (loss)		$ 15,318	$ (3,446)	$ 25,984					$ 22,538	$ 37,855	$ 28,750	$ (49,809)	$ (34,459)
Net income (loss) per share attributed to PAE Incorporated:
Basic (in dollars per share)		$ 0.17	$ (0.04)	$ 0.43					$ 0.30	$ 0.47	$ 0.34	$ (2.36)	$ (1.63)
Diluted (in dollars per share)		$ 0.16	$ (0.04)	$ 0.43					$ 0.30	$ 0.46	$ 0.34	$ (2.36)	$ (1.63)
Weighted average shares outstanding:
Basic (in shares)		92,070,306	92,044,098	59,807,549					75,890,028	81,323,258	84,114,016	21,127,823	21,127,823
Diluted (in shares)		93,392,565	92,787,379	59,807,549					76,273,931	82,115,825	85,369,328	21,127,823	21,127,823