Supplementary Balance Sheet Information - Prepaid Expenses and Other Current Assets (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Supplementary Balance Sheet Information
Prepaid expenses	$ 81,483	$ 84,173
Supplies inventory	14,027	17,105
Income taxes receivable	3,238
Other	58,577	63,210
Total	$ 157,325	$ 164,488