Accounting Policies (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended												12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Research expense													$ 29,800	$ 30,700	$ 28,800
Capitalized salaries, travel, and consulting costs related to software development													1,200	1,200
Defined benefit pension plan assets	$ 14,200				$ 16,200								14,200	16,200
Gross profit	87,900	$ 92,400	$ 91,700	$ 77,700	77,500	$ 79,600	$ 63,200	$ 76,000	$ 77,500	$ 72,600	$ 78,500	$ 72,700	349,749	296,283	301,284
Cumulative adjustment to accounts receivable on reclassification													8,500
Contract assets receivable	$ 47,400												47,400
Recorded Charge on BR contract							15,800						632,730	567,434	478,555
Inventory write off							4,000
Reduction to Cost of goods sold													4,900
Write-off deferred contract costs
Reserve for additional anticipated losses							$ 11,800
Interest rate on contract receivables	2.00%												2.00%
Extended payment term of receivables													Over a 10 year period starting in 2020
Percentage of estimate revenue of services													5.00%
Contracts Accounted for under Percentage of Completion [Member]
Gross profit													$ (500)	(600)	$ 1,500
Long term contract [Member]
Gross profit	$ 1,500
Unfavorable adjustment charge due to ramp-up inefficiencies	400				400
Financial Assets [Member]
Defined benefit pension plan assets	5,300				1,300								5,300	1,300
Russia Entity [Member]
Equity method investment	$ 400				$ 500								$ 400	$ 500