Accounts Payable, Accrued, and Other Liabilities - Accounts Payable and Accrued Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Payables and Accruals [Abstract]
Accounts payable	$ 37,508	$ 49,000
Payroll and employee benefits payable	143,803	120,278
Severance and retention bonus payable	28,292	44,685
Bonus payable	170,719	162,710
Commissions payable	126,844	108,969
Taxes payable	19,725	46,758
Other accrued liabilities	183,222	134,421
Total accounts payable and accrued liabilities	$ 710,113	$ 666,821