Business Segments and Geographic Information - Income Reconciliation (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2015
Pre-Tax Income Reconciliation of Segments
Total operating income from segments	$ 54,553	$ 65,957	$ 118,925	$ 125,124
Unallocated Amount:
General and Administrative Expenses	(52,206)	(36,904)	(94,792)	(70,965)
Loss on extinguishment of debt	0	(15,866)	0	(15,866)	$ (15,866)
Income before income taxes and equity in earnings of affiliates	30,916	24,904	72,265	59,262
Operating Segments
Pre-Tax Income Reconciliation of Segments
Total operating income from segments	106,759	102,861	213,717	196,089
Segment Reconciling Items
Unallocated Amount:
General and Administrative Expenses	(52,206)	(36,904)	(94,792)	(70,965)
Net Interest Expense	(23,637)	(25,187)	(46,660)	(49,996)
Loss on extinguishment of debt	$ 0	$ (15,866)	$ 0	$ (15,866)