Fair Value of Financial Instruments (Tables)

9 Months Ended

Sep. 30, 2015

Fair Value Disclosures [Abstract]

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

Cash, cash equivalents and short-term investments consist of the following:

	September 30, 2015			December 31, 2014
	Cost		Fair Value	Cost	Fair Value
Cash and Cash Equivalents:
Cash and overnight deposits	$	487,243	487,243	531,312	531,312
Corporate commercial paper	430,387		430,428	356,468	356,536
Time deposits	51,053		51,053	39,327	39,327
Total cash and cash equivalents	968,683		968,724	927,107	927,175
Short-Term Investments:
Corporate commercial paper	8,239		8,245	40,295	40,350
Time deposits	21		21	41	41
Total short-term investments	8,260		8,266	40,336	40,391
Total	$	976,943	976,990	967,443	967,566