Accounts Payable and Accrued Expenses - Schedule of Accounts Payable and Accrued Expenses (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Payables And Accruals [Abstract]
Accounts payable	$ 18,605	$ 13,812
Accrued salaries and bonuses	189,439	160,495
Accrued payroll taxes and benefits	43,403	36,176
Accrued professional liability risks	19,324	17,466
Accrued contingent consideration	19,833	16,109
Other accrued expenses	18,150	11,603
Accounts payable and accrued expenses, total	$ 308,754	$ 255,661