Fair Value of Financial Instruments (Tables)

6 Months Ended

Jun. 30, 2019

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, 2019				December 31, 2018
	Cost		Fair Value		Cost		Fair Value
Cash and Cash Equivalents:
Cash and overnight deposits	$	513,328	$	513,328	$	427,307	$	427,307
Corporate commercial paper		530,565		530,991		467,300		467,760
Time deposits		38,757		38,757		29,128		29,128
Total cash and cash equivalents	$	1,082,650	$	1,083,076	$	923,735	$	924,195