Accounts Payable and Accrued Expenses - Schedule of Accounts Payable and Accrued Expenses (Detail) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Payables and Accruals [Abstract]
Accounts payable	$ 60,956	$ 35,410
Accrued salaries and bonuses	158,579	193,631
Accrued payroll taxes and benefits	48,474	54,768
Accrued professional liabilities	55,469	44,699
Accrued interest	26,940	32,910
Other accrued expenses	38,099	49,219
Accounts payable and accrued expenses, total	$ 388,517	$ 410,637