Overview and Basis of Presentation - Impact of Adopting ASU 2017-07 on Condensed Consolidated Statement of Operations (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Costs of services		$ 257,295	$ 280,638
Costs of products		31,122	32,102
Corporate activities		2,217	2,541
Other expense	[1]	$ 238	452
Reclassifications to Conform with Revenue Presentation
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Costs of services			7,412
Costs of products			(7,412)
As Previously Reported
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Costs of services			273,609
Costs of products			39,514
Corporate activities			2,610
ASU 2017-07
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Costs of services			(383)
Corporate activities			(69)
Other expense			$ 452

[1] We adopted ASU 2017-07 on January 1, 2018, which requires retrospective adoption. As a result, we recorded the nonservice cost component of net periodic benefit cost within other expense for the three months ended March 31, 2018, and we reclassified $0.5 million from operating expenses to other expense for the three months ended March 31, 2017 to conform with current period presentation. Refer to Note 1 – Overview and Basis of Presentation for additional details on the impact of this adoption on our Condensed Consolidated Statements of Operations.