Fair Value of Financial Instruments (Tables)

3 Months Ended

Mar. 31, 2014

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:

	March 31, 2014			December 31, 2013
	Cost		Fair Value	Cost	Fair Value
Cash and Cash Equivalents:
Cash and overnight deposits	$	584,552	584,552	590,317	590,317
Corporate commercial paper	506,872		506,958	629,923	629,990
Time deposits	39,622		39,622	27,412	27,412
Total cash and cash equivalents	1,131,046		1,131,132	1,247,652	1,247,719
Short-Term Investments:
Corporate commercial paper	86,449		86,521	26,296	26,321
Time deposits	42		42	41	41
Total short-term investments	86,491		86,563	26,337	26,362
Total	$	1,217,537	1,217,695	1,273,989	1,274,081