Accrued Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Summary of accrued liabilities
Accrued payroll and other employee related expenses	$ 383,356	$ 176,379
Contract liabilities	165,731	58,455
Accrued business taxes	89,854	46,717
Income taxes payable	78,422	12,236
Self-insurance reserves	74,034	38,642
Accrued rebates payable	40,961	18,592
Accrued interest	26,078	13,567
Other	71,753	20,948
Total accrued liabilities	$ 930,189	$ 385,536