Fair Value of Financial Instruments (Tables)

3 Months Ended

Mar. 31, 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:

	March 31, 2019				December 31, 2018
	Cost		Fair Value		Cost		Fair Value
Cash and Cash Equivalents:
Cash and overnight deposits	$	460,584	$	460,584	$	427,307	$	427,307
Corporate commercial paper	692,669		693,248		467,300		467,760
Time deposits	36,176		36,176		29,128		29,128
Total cash and cash equivalents	$	1,189,429	$	1,190,008	$	923,735	$	924,195