Fair Value of Financial Instruments (Tables)

9 Months Ended

Sep. 30, 2017

Fair Value Disclosures [Abstract]

Schedule of Fair value of Cash and Cash Equivalents by Balance Sheet Grouping

Cash and cash equivalents consist of the following:

	September 30, 2017			December 31, 2016
	Cost		Fair Value	Cost	Fair Value
Cash and Cash Equivalents:
Cash and overnight deposits	$	385,432	385,432	406,787	406,787
Corporate commercial paper	613,433		613,825	507,777	507,889
Time deposits	34,579		34,579	59,871	59,871
Total cash and cash equivalents	$	1,033,444	1,033,836	974,435	974,547