Segments (Reconciliation of adjusted EBITDA to consolidated financial statements) (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2020	Mar. 31, 2019
Segment Reporting, Revenue Reconciling Item [Line Items]
Income before income taxes		$ 29,493	$ 26,350
Interest expense		5,932	6,038
Interest income		(583)	(941)
Depreciation and amortization		19,995	16,792
Merger and integration costs		1,168	2,790
Non-cash stock compensation expense		3,170	2,915
Acquisition costs		1,831	580
Other items	[1]	0	(124)
Other reconciling items [Member] | Other reconciling items [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Depreciation and amortization		494	645
Adjusted EBITDA		19,370	19,368
Operating segments [Member] | Geographic divisions [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Depreciation and amortization		19,501	16,147
Adjusted EBITDA		$ (80,376)	$ (73,768)

[1] Represents the effect of the settlement of pending litigation for an amount below what was previously accrued.