Leases (Supplemental Information Relating to Operating Leases) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Jan. 01, 2019
Leases [Abstract]
Lease expense incurred: Operating lease cost	$ 4,562
Operating lease right of use assets	57,013	$ 60,325
Operating lease liabilities	62,938	$ 66,551
Operating cash flows from operating leases	$ 4,304
Weighted average remaining operating lease term	5 years 6 months
Weighted average discount rate on operating leases	4.48%