Commitments and Contingencies (Narrative) (Details) $ / Person in Thousands, $ in Thousands	9 Months Ended
	Sep. 30, 2017 USD ($) $ / Person	Sep. 30, 2016 USD ($)
Commitments and Contingencies [Line Items]
Rent expense, operating leases	$ 4,300	$ 4,700
Reduction of rent expense as a result of purchase accounting adjustment	(948)	$ 0
Self-insured health insurance, liability	$ 332
Maximum [Member]
Commitments and Contingencies [Line Items]
Self-insured health insurance limit, per person | $ / Person	120
Self-insured health Insurance, aggregate liability based on participants and claims (percentage)	125.00%
Self-insured health insurance, estimated cumulative liability for annual contract	$ 2,800
Computer Equipment [Member] | Minimum [Member]
Commitments and Contingencies [Line Items]
Capital lease obligation, term	3 years
Computer Equipment [Member] | Maximum [Member]
Commitments and Contingencies [Line Items]
Capital lease obligation, term	5 years