Property and Equipment (Components Of Property and Equipment) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 173,920	$ 156,901
Less: Accumulated depreciation	(116,824)	(102,224)
Property and equipment, net	57,096	54,677
Equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	88,189	78,614
Computer Software
Property, Plant and Equipment [Line Items]
Property and equipment, gross	34,994	30,867
Building and Building Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	26,423	25,472
Leasehold Improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	13,316	11,571
Furniture
Property, Plant and Equipment [Line Items]
Property and equipment, gross	9,239	8,618
Land
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 1,759	$ 1,759
Minimum [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful lives (years)	1 year
Minimum [Member] | Equipment
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful lives (years)	1 year
Minimum [Member] | Computer Software
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful lives (years)	1 year
Minimum [Member] | Building and Building Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful lives (years)	5 years
Minimum [Member] | Leasehold Improvements
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful lives (years)	1 year
Minimum [Member] | Furniture
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful lives (years)	1 year
Maximum [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful lives (years)	40 years
Maximum [Member] | Equipment
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful lives (years)	10 years
Maximum [Member] | Computer Software
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful lives (years)	5 years
Maximum [Member] | Building and Building Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful lives (years)	40 years
Maximum [Member] | Leasehold Improvements
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful lives (years)	16 years
Maximum [Member] | Furniture
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful lives (years)	13 years