Furniture, Equipment and Leasehold Improvements, Net (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Furniture, equipment and leasehold improvements [Abstract]
Furniture, equipment and leasehold improvements, gross	$ 797,343	$ 783,011
Less: Accumulated depreciation and amortization	(639,774)	(623,447)
Furniture, equipment and leasehold improvements, net	157,569	159,564
Furniture and Equipment [Member]
Furniture, equipment and leasehold improvements [Abstract]
Furniture, equipment and leasehold improvements, gross	551,502	535,890
Leasehold Improvements [Member]
Furniture, equipment and leasehold improvements [Abstract]
Furniture, equipment and leasehold improvements, gross	$ 245,841	$ 247,121