Segments (Reconciliation of adjusted EBITDA to consolidated financial statements) (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2019	Mar. 31, 2018
Segment Reporting, Revenue Reconciling Item [Line Items]
Income before income taxes		$ 26,350	$ 19,998
Interest expense		6,038	5,982
Interest income		(941)	0
Depreciation and amortization		16,792	15,681
Merger and integration costs		2,790	1,687
Non-cash stock compensation expense		2,915	1,775
Acquisition costs		580	234
Other items	[1]	(124)	1,823
Other reconciling items [Member] | Other reconciling items [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Depreciation and amortization		645	470
Adjusted EBITDA		19,368	16,494
Operating segments [Member] | Geographic divisions [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Depreciation and amortization		16,147	15,211
Adjusted EBITDA		$ (73,768)	$ (63,674)

[1] For the three months ended March 31, 2019, represents the effect of the settlement of pending litigation for an amount below what was previously accrued. See Note 9 for further details. For the three months ended March 31, 2018, represents costs incurred in connection with the departure of the Company’s former chief executive officer and the search for his permanent replacement.