Leases Leases (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Jan. 01, 2019
Lessee, Lease, Description [Line Items]
Lease Of Facilities And Furniture Maximum Duration	15 years
Operating Lease, Right-of-Use Asset	$ 243,400	$ 243,700
Operating Leases, Rent Expense, Net	$ 16,900
Operating Lease, Weighted Average Discount Rate, Percent	3.40%
Operating Lease, Weighted Average Remaining Lease Term	8 years 11 months
LeaseLiabilityPaymentsDueWithinTwelveMonths	$ 43,921
Lessee, Operating Lease, Liability, Payments, Due Year Two	45,531
Lessee, Operating Lease, Liability, Payments, Due Year Three	40,744
Lessee, Operating Lease, Liability, Payments, Due Year Four	35,123
Lessee, Operating Lease, Liability, Payments, Due Year Five	28,426
Lessee, Operating Lease, Liability, Payments, Due after Year Five	123,222
Lessee, Operating Lease, Liability, Payments, Due	316,967
Lessee, Operating Lease, Liability, Undiscounted Excess Amount	(45,032)
Operating Lease, Liability	$ 271,935	$ 264,600