Commitments Contingencies and Guarantees (Schedule of Future Minimum Rental Payments for Operating Leases) (Details) - Property Subject to Operating Lease [Member] $ in Thousands	Dec. 31, 2018 USD ($)
Operating Leases, Future Minimum Payments Due [Abstract]
Operating Leases, Future Minimum Payments Due, Current	$ 13,578
Operating Leases, Future Minimum Payments, Due in Two Years	11,541
Operating Leases, Future Minimum Payments, Due in Three Years	9,447
Operating Leases, Future Minimum Payments, Due in Four Years	8,587
Operating Leases, Future Minimum Payments, Due in Five Years	8,248
Operating Leases, Future Minimum Payments, Due Thereafter	$ 14,101