Leases Leases (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2019	Jan. 01, 2019
Lessee, Lease, Description [Line Items]
Lease Of Facilities And Furniture Maximum Duration		15 years
Operating Lease, Right-of-Use Asset	$ 237,400	$ 237,400	$ 243,700
Operating Leases, Rent Expense, Net	$ 17,800	$ 33,300
Operating Lease, Weighted Average Discount Rate, Percent	3.30%	3.30%
Operating Lease, Weighted Average Remaining Lease Term	8 years 6 months	8 years 6 months
LeaseLiabilityPaymentsDueWithinTwelveMonths	$ 27,505	$ 27,505
Lessee, Operating Lease, Liability, Payments, Due Year Two	46,088	46,088
Lessee, Operating Lease, Liability, Payments, Due Year Three	41,748	41,748
Lessee, Operating Lease, Liability, Payments, Due Year Four	35,556	35,556
Lessee, Operating Lease, Liability, Payments, Due Year Five	30,469	30,469
Lessee, Operating Lease, Liability, Payments, Due after Year Five	122,095	122,095
Lessee, Operating Lease, Liability, Payments, Due	303,461	303,461
Lessee, Operating Lease, Liability, Undiscounted Excess Amount	(41,741)	(41,741)
Operating Lease, Liability	$ 261,720	$ 261,720	$ 264,600