Fair Value of Financial Instruments (Tables)

6 Months Ended

Jun. 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:

	June 30, 2017			December 31, 2016
	Cost		Fair Value	Cost	Fair Value
Cash and Cash Equivalents:
Cash and overnight deposits	$	496,126	496,126	406,787	406,787
Corporate commercial paper	573,722		574,037	507,777	507,889
Time deposits	45,062		45,062	59,871	59,871
Total cash and cash equivalents	$	1,114,910	1,115,225	974,435	974,547