Acquisitions (Narrative) (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016	Jun. 30, 2016
Business Acquisition [Line Items]
Contingent consideration liability	$ 1,580	$ 2,211
Goodwill	15,794	15,794	$ 15,482
Challenger And Hybrid [Member]
Business Acquisition [Line Items]
Acquisition purchase price		22,800
Contingent consideration liability		6,000
Cash		1,200
Intangible assets		9,900
Net liabilities assumed		1,200
Goodwill		12,900
Challenger And Hybrid [Member] | Other Long-Term Liabilities [Member]
Business Acquisition [Line Items]
Contingent consideration liability	1,200	1,700
Challenger And Hybrid [Member] | Accrued Expenses And Other Current Liabilities [Member]
Business Acquisition [Line Items]
Contingent consideration liability	$ 400	$ 500