Derivatives and Hedging Activities - Derivatives Not Designated as Hedging Instruments (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivatives not designated as hedging instruments, gain (loss)	$ 10,561	$ 50,237	$ 19,762	$ 44,202
Embedded derivatives [Member] | Revenues [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivatives not designated as hedging instruments, gain (loss)	(185)	3,909	722	1,464
Economic hedge of embedded derivatives [Member] | Revenues [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivatives not designated as hedging instruments, gain (loss)	598	(1,468)	541	(938)
Foreign currency forward contract [Member] | Other income (expense) [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivatives not designated as hedging instruments, gain (loss)	$ 10,148	$ 47,796	$ 18,499	$ 43,676