Supplementary Balance Sheet Information - Cash and Cash Equivalent Balances (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Cash and Cash Equivalents [Abstract]
Cash and cash equivalents in domestic accounts	$ 399,633	$ 307,578
Cash and cash equivalents in foreign accounts	47,250	81,750
Cash and cash equivalents	$ 446,883	$ 389,328