Composition of Certain Financial Statement Captions (Property And Equipment) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Property and Equipment, gross	$ 456,383	$ 431,512
Less: Accumulated depreciation	(309,955)	(285,322)
Property and Equipment, net	146,428	146,190
Depreciation expense	27,311	26,440	$ 24,044
Buildings [Member]
Property, Plant and Equipment [Line Items]
Property and Equipment, gross	153,961	152,171
Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and Equipment, gross	115,546	106,759
Land [Member]
Property, Plant and Equipment [Line Items]
Property and Equipment, gross	10,030	10,030
Purchased software [Member]
Property, Plant and Equipment [Line Items]
Property and Equipment, gross	134,610	128,008
Furniture and fixtures [Member]
Property, Plant and Equipment [Line Items]
Property and Equipment, gross	18,114	17,292
Leasehold improvements [Member]
Property, Plant and Equipment [Line Items]
Property and Equipment, gross	18,017	15,175
Construction in progress [Member]
Property, Plant and Equipment [Line Items]
Property and Equipment, gross	$ 6,105	$ 2,077