Revenue Recognition and Related Balance Sheet Accounts - Revenue Disaggregated by Geographic Location and Contract Type (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Disaggregation of Revenue [Line Items]
Revenues	$ 12,980,213	$ 11,202,672	$ 12,112,153
Percentage of total revenues	100.00%	100.00%	100.00%
Unit-price contracts
Disaggregation of Revenue [Line Items]
Revenues	$ 5,029,100	$ 4,172,363	$ 4,193,295
Percentage of total revenues	38.70%	37.20%	34.60%
Cost-plus contracts
Disaggregation of Revenue [Line Items]
Revenues	$ 3,102,075	$ 2,649,770	$ 3,304,161
Percentage of total revenues	23.90%	23.70%	27.30%
Fixed price contracts
Disaggregation of Revenue [Line Items]
Revenues	$ 4,849,038	$ 4,380,539	$ 4,614,697
Percentage of total revenues	37.40%	39.10%	38.10%
United States
Disaggregation of Revenue [Line Items]
Revenues	$ 11,068,493	$ 9,618,951	$ 10,190,684
Percentage of total revenues	85.30%	85.80%	84.00%
Canada
Disaggregation of Revenue [Line Items]
Revenues	$ 1,557,117	$ 1,252,365	$ 1,436,720
Percentage of total revenues	12.00%	11.20%	11.90%
Australia
Disaggregation of Revenue [Line Items]
Revenues	$ 221,038	$ 200,664	$ 187,915
Percentage of total revenues	1.70%	1.80%	1.60%
Others
Disaggregation of Revenue [Line Items]
Revenues	$ 133,565	$ 130,692	$ 296,834
Percentage of total revenues	1.00%	1.20%	2.50%