Business Segments and Geographic Information (Details 1) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Pre-Tax Income Reconciliation of Segments
Total operating income from segments	$ 53,281	$ 60,889	$ 105,952	$ 109,459
Unallocated Amount:
General and Administrative Expenses	(32,174)	(28,148)	(64,022)	(56,650)
Income before income taxes and equity in earnings of affiliates	29,498	41,111	59,596	69,761
Operating Segments
Pre-Tax Income Reconciliation of Segments
Total operating income from segments	85,455	89,037	169,974	166,109
Segment Reconciling Items
Unallocated Amount:
General and Administrative Expenses	(32,174)	(28,148)	(64,022)	(56,650)
Net Interest Expense	$ (23,783)	$ (19,778)	$ (46,356)	$ (39,698)