Business Segments and Geographic Information - Income Reconciliation (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Pre-Tax Income Reconciliation of Segments
Operating income from segments	$ 78,159	$ 69,780	$ 234,111	$ 201,181
Unallocated Amount:
General and Administrative Expenses	(48,488)	(47,647)	(142,183)	(136,927)
Gain (loss) on extinguishment of debt	594	0	(5,147)	(574)
Income before income taxes and equity in earnings of affiliates	48,794	40,217	136,234	116,596
Operating Segments
Pre-Tax Income Reconciliation of Segments
Operating income from segments	126,647	117,427	376,294	338,108
Segment Reconciling Items
Unallocated Amount:
General and Administrative Expenses	(48,488)	(47,647)	(142,183)	(136,927)
Net Interest Expense	(29,959)	(29,563)	(92,730)	(84,011)
Gain (loss) on extinguishment of debt	$ 594	$ 0	$ (5,147)	$ (574)