Revenue Recognition (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Jan. 01, 2018	Dec. 31, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Retained earnings	$ (4,114,472)		$ (4,049,965)
Other current liabilities	$ 1,098,916		$ 1,034,441
Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Accounting Standards Update 2014-09 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Retained earnings		$ 8,000
Other current liabilities		$ 8,000