Investments in Affiliates (Equity Method Investment, Summarized Financial Data) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Summary Financial Data:
Current assets	$ 741,714		$ 741,714		$ 628,125
Total assets	4,068,167		4,068,167		3,942,847
Current liabilities	118,201		118,201		139,401
Long-term debt, including current portion	2,756,055		2,756,055		2,764,599
Total liabilities	3,464,565		3,464,565		3,474,504
Shareholders' equity	603,602		603,602		$ 468,343
Revenues	172,995	$ 164,114	340,639	$ 348,980
Operating expenses	(30,405)	(26,933)	(68,384)	(57,536)
Depreciation, amortization and stock-based compensation	(54,093)	(48,287)	(107,891)	(96,786)
Other operating income (expense)	(10)	(15)	(65)	(13)
Operating income	88,487	88,879	164,299	194,645
Interest expense	(46,492)	(42,520)	(93,335)	(87,608)
Foreign exchange (loss) gain	45,946	(45,777)	98,415	(109,078)
Gain (loss) on financial instruments	(21,263)	(1,767)	(36,375)	30,616
Other income (expense)	4,272	2,973	8,106	4,591
Income tax provision	(6,481)	(7,815)	(11,036)	(31,585)
Net (loss) income	$ 64,469	$ (6,027)	$ 130,074	$ 1,581