Supplementary Balance Sheet Information - Prepaid Expenses and Other Current Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Supplementary Balance Sheet Information
Prepaid expenses	$ 69,708	$ 84,173
R&D state tax credit	22,642
Supplies inventory	13,174	17,105
Income taxes receivable	1,595
Other	68,930	63,210
Total	$ 176,049	$ 164,488