Leased Assets and Liabilities (Lease Expense) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Leases [Abstract]
Operating lease expense	$ 12,091	$ 12,277
Amortization of leased assets	880	602
Interest on lease liabilities	172	118
Variable lease expense	5,864	5,142
Sublease income	(666)	(249)
Total expense	$ 18,341	$ 17,890