Accounting Policies (Narrative) (Details) - USD ($)
$ in Thousands

3 Months Ended

12 Months Ended

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, 2015

Sep. 30, 2015

Jun. 30, 2015

Mar. 31, 2015

Dec. 31, 2017

Dec. 31, 2016

Dec. 31, 2015

Research expense

$ 30,700

$ 28,800

$ 31,700

Capitalized salaries, travel, and consulting costs related to software development

1,200

1,200

Defined benefit pension plan assets

$ 16,200

$ 7,800

16,200

7,800

Gross profit

$ 77,400

$ 79,400

$ 63,100

$ 75,900

77,400

$ 72,400

$ 78,300

$ 72,500

$ 71,700

$ 75,700

$ 54,600

$ 76,700

295,780

300,568

278,686

Recorded Charge on BR contract

15,800

14,000

Inventory write off

4,000

Reduction to Cost of goods sold

$ 4,900

Write-off deferred contract costs

10,900

Reserve for additional anticipated losses

$ 11,800

3,100

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%

Increase/(Decrease) in operating cash flows due to change affecting cash payments of taxes in lieu of share issuance

$ 1,300

1,400

Increase/(Decrease) in financing cash flows due to change affecting cash payments of taxes in lieu of share issuance

(1,300)

(1,400)

Increase/(Decrease) in operating cash flows due to change affecting classification of excess tax benefits

100

100

Increase/(Decrease) in financing cash flows due to change affecting classification of excess tax benefits

(100)

(100)

Contracts Accounted for under Percentage of Completion [Member]

Gross profit

(600)

1,500

$ 400

Financial Assets [Member]

Defined benefit pension plan assets

$ 1,300

6,500

1,300

6,500

Russia Entity [Member]

Equity method investment

$ 500

$ 400

$ 500

$ 400