Segments (Reconciliation of adjusted EBITDA to consolidated financial statements) (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017
Segment Reporting, Revenue Reconciling Item [Line Items]
Income before income taxes		$ 19,998	$ 4,717
Interest expense		5,982	6,088
Depreciation and amortization		15,681	16,813
Merger and integration costs		1,687	4,441
Non-cash stock compensation expense		1,775	1,231
Acquisition costs		234	273
Other items	[1]	1,823	0
Other reconciling items [Member] | Other reconciling items [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Depreciation and amortization		470	586
Adjusted EBITDA		16,494	13,840
Operating segments [Member] | Geographic divisions [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Depreciation and amortization		15,211	16,227
Adjusted EBITDA		$ (63,674)	$ (47,403)

[1] Represents severance and executive search costs incurred in connection with the departure of the Company’s former chief executive officer and the search for his permanent replacement.