Operating Expenses (Schedule of Depreciation and Amortization Expenses) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating Expenses [Abstract]
Depreciation expense	$ 28,337	$ 30,983	$ 35,374
Amortization expense	24,357	9,878	6,658
Total depreciation and amortization expenses	$ 52,694	$ 40,861	$ 42,032