Supplementary Balance Sheet Information - Prepaid Expenses and Other Current Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Supplementary Balance Sheet Information
Prepaid expenses	$ 80,646	$ 84,173
Supplies inventory	15,706	17,105
Other	83,973	63,210
Total	$ 180,325	$ 164,488