Segment Information, Revenue by Major Market (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($) Market	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Segment Information [Abstract]
Number of major markets | Market	3
Number of markets | Market	50
Segment Contribution [Abstract]
Revenue	$ 2,679,008	$ 2,279,099	$ 2,207,797
Major Market [Member] | Mainland China [Member]
Segment Contribution [Abstract]
Revenue	886,472	716,991	610,414
Major Market [Member] | South Korea [Member]
Segment Contribution [Abstract]
Revenue	373,357	361,692	413,696
Major Market [Member] | Japan [Member]
Segment Contribution [Abstract]
Revenue	254,939	256,085	279,042
Major Market [Member] | United States [Member]
Segment Contribution [Abstract]
Revenue	311,436	218,734	201,239
Major Market [Member] | All Others [Member]
Segment Contribution [Abstract]
Revenue	$ 852,804	$ 725,597	$ 703,406