Fair Value of Financial Instruments (Tables)

12 Months Ended

Dec. 31, 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:

	December 31, 2015			December 31, 2014
	Cost		Fair Value	Cost	Fair Value
Cash and cash equivalents:
Cash and overnight deposits	$	445,582	445,582	531,312	531,312
Corporate commercial paper	302,433		302,480	356,468	356,536
Time deposits	59,781		59,781	39,327	39,327
Total cash and cash equivalents	807,796		807,843	927,107	927,175
Short-term investments:
Corporate commercial paper	—		—	40,295	40,350
Time deposits	40		40	41	41
Total short-term investments	40		40	40,336	40,391
Total	$	807,836	807,883	967,443	967,566