Investments in Affiliates (Equity Method Investment, Summarized Financial Data) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Summary Financial Data:
Current assets	$ 808,838		$ 808,838		$ 628,125
Total assets	4,050,816		4,050,816		3,942,847
Current liabilities	118,149		118,149		139,401
Long-term debt, including current portion	2,753,787		2,753,787		2,764,599
Total liabilities	3,437,807		3,437,807		3,474,504
Shareholders' equity	613,009		613,009		$ 468,343
Revenues	180,180	$ 174,010	520,819	$ 522,990
Operating expenses	(26,443)	(34,268)	(94,827)	(91,804)
Depreciation, amortization and stock-based compensation	(54,854)	(47,946)	(162,745)	(144,732)
Other operating income (expense)	(45)	848	(110)	835
Operating income	98,838	92,644	263,137	287,289
Interest expense	(46,239)	(43,063)	(139,574)	(130,671)
Foreign exchange (loss) gain	(24,702)	42,784	73,713	(66,294)
Gain (loss) on financial instruments	(4,244)	(202)	(40,619)	30,414
Other income (expense)	4,497	3,204	12,603	7,795
Income tax provision	(15,548)	(7,605)	(26,584)	(39,190)
Net (loss) income	$ 12,602	$ 87,762	$ 142,676	$ 89,343