Net Income Per Share - Computation of Basic and Diluted Loss Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 26, 2021	Sep. 27, 2020	Sep. 26, 2021	Sep. 27, 2020
Numerator:
Net income attributed to PAE Incorporated	$ 29,789	$ 15,318	$ 57,523	$ 37,855
Denominator:
Basic weighted average shares (in shares)	93,122,414	92,070,306	92,949,301	81,323,258
Diluted weighted average shares (in shares)	95,836,986	93,392,565	95,599,019	82,115,825
Basic income per share (in dollars per share)	$ 0.32	$ 0.17	$ 0.62	$ 0.47
Diluted income per share (in dollars per share)	$ 0.31	$ 0.16	$ 0.60	$ 0.46