Accounts Payable and Accrued Expenses - Schedule of Accounts Payable and Accrued Expenses (Detail) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Payables and Accruals [Abstract]
Accounts payable	$ 40,658	$ 59,771
Accrued salaries and incentive compensation	129,915	184,849
Accrued payroll taxes and benefits	35,669	43,945
Accrued professional liabilities	36,473	50,607
Accrued interest	29,280	32,721
Other accrued expenses	57,923	51,290
Accounts payable and accrued expenses, total	$ 329,918	$ 423,183