Consolidated Statements of Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Income Statement [Abstract]
Revenue	$ 879,356	$ 979,459	$ 1,754,053	$ 1,950,452
Direct cost of contracts	680,328	749,324	1,349,410	1,518,956
Equity in earnings of unconsolidated joint ventures	9,428	3,769	16,958	9,883
Selling, general and administrative expenses	188,238	187,640	375,760	371,414
Operating income	20,218	46,264	45,841	69,965
Interest income	152	196	250	424
Interest expense	(4,910)	(4,159)	(9,451)	(8,181)
Other income (expense), net	405	715	(1,386)	263
Total other income (expense)	(4,353)	(3,248)	(10,587)	(7,494)
Income before income tax expense	15,865	43,016	35,254	62,471
Income tax expense	(3,838)	(11,891)	(9,213)	(16,975)
Net income including noncontrolling interests	12,027	31,125	26,041	45,496
Net income attributable to noncontrolling interests	(5,325)	(7,826)	(10,300)	(9,224)
Net income attributable to Parsons Corporation	$ 6,702	$ 23,299	$ 15,741	$ 36,272
Earnings per share:
Basic	$ 0.07	$ 0.23	$ 0.15	$ 0.36
Diluted	$ 0.06	$ 0.23	$ 0.15	$ 0.36