Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2017

Commitments and Contingencies Disclosure [Abstract]

Future Minimum Rental Commitments under Office and Equipment Leases

Future minimum rental commitments under such office and equipment leases as of December 31, 2017 are as follows:

(Expressed in thousands)
2018	$	43,727
2019	39,110
2020	30,452
2021	26,053
2022	22,998
2023 and thereafter	87,729
	$	250,069