Fair Value Measurements - Carrying Amount and Estimated Fair Value of Financial Instrument Assets and Liabilities which are Not Measured at Fair Value (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Level 1 [Member]
Financial Assets:
Cash and Cash Equivalents	$ 451,871	$ 575,317
Certificates of Deposit, at Carrying Value	0	0
Receivables(1)	0	0
Contract Assets(2)	0	0
Receivable from Employees and Related Parties	0	0
Financial Liabilities:
Accounts Payable and Accrued Expenses	0	0
Payable to Employees and Related Parties	0	0
Notes Payable(3)	0	0
Level 2 [Member]
Financial Assets:
Cash and Cash Equivalents	0	0
Certificates of Deposit, at Carrying Value	157,313	141,218
Receivables(1)	386,703	436,749
Contract Assets(2)	52,314	25,986
Receivable from Employees and Related Parties	23,722	25,208
Financial Liabilities:
Accounts Payable and Accrued Expenses	32,443	31,633
Payable to Employees and Related Parties	58,947	58,876
Notes Payable(3)	364,821	390,288
Level 3 [Member]
Financial Assets:
Cash and Cash Equivalents	0	0
Certificates of Deposit, at Carrying Value	0	0
Receivables(1)	0	0
Contract Assets(2)	0	0
Receivable from Employees and Related Parties	0	0
Financial Liabilities:
Accounts Payable and Accrued Expenses	0	0
Payable to Employees and Related Parties	0	0
Notes Payable(3)	0	0
Carrying Amount [Member]
Financial Assets:
Cash and Cash Equivalents	451,871	575,317
Certificates of Deposit, at Carrying Value	157,313	141,218
Receivables(1)	388,900	439,432
Contract Assets(2)	53,119	27,037
Receivable from Employees and Related Parties	23,722	25,208
Financial Liabilities:
Accounts Payable and Accrued Expenses	32,443	31,633
Payable to Employees and Related Parties	58,947	58,876
Notes Payable(3)	375,361	376,243
Total [Member]
Financial Assets:
Cash and Cash Equivalents	451,871	575,317
Certificates of Deposit, at Carrying Value	157,313	141,218
Receivables(1)	386,703	436,749
Contract Assets(2)	52,314	25,986
Receivable from Employees and Related Parties	23,722	25,208
Financial Liabilities:
Accounts Payable and Accrued Expenses	32,443	31,633
Payable to Employees and Related Parties	58,947	58,876
Notes Payable(3)	364,821	390,288
Equity Securities [Member] | Level 1 [Member]
Financial Assets:
Investments	0	0
Equity Securities [Member] | Level 2 [Member]
Financial Assets:
Investments	0	0
Equity Securities [Member] | Level 3 [Member]
Financial Assets:
Investments	656	676
Equity Securities [Member] | Carrying Amount [Member]
Financial Assets:
Investments	656	676
Equity Securities [Member] | Total [Member]
Financial Assets:
Investments	$ 656	$ 676