Commitments Contingencies and Guarantees (Schedule of Future Minimum Rental Payments for Operating Leases) (Details) - Property Subject to Operating Lease [Member] $ in Thousands	Dec. 31, 2017 USD ($)
Operating Leases, Future Minimum Payments Due [Abstract]
Operating Leases, Future Minimum Payments Due, Current	$ 11,157
Operating Leases, Future Minimum Payments, Due in Two Years	7,108
Operating Leases, Future Minimum Payments, Due in Three Years	4,879
Operating Leases, Future Minimum Payments, Due in Four Years	3,076
Operating Leases, Future Minimum Payments, Due in Five Years	2,421
Operating Leases, Future Minimum Payments, Due Thereafter	$ 9,466