Fair Value of Financial Instruments (Tables)

6 Months Ended

Jun. 30, 2013

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:

	June 30, 2013				December 31, 2012
	Cost		Fair Value		Cost		Fair Value
Cash and Cash Equivalents:
Cash and overnight deposits	$	526,256	$	526,256	$	458,169	$	458,169
Corporate commercial paper	634,087		634,162		642,884		642,886
Time deposits	125,766		125,766		159,789		159,789
Total cash and cash equivalents	$	1,286,109	$	1,286,184	$	1,260,842	$	1,260,844
Short-Term Investments:
Corporate commercial paper	89,811		89,815		—		—
Time deposits	91		91		139		139
Total short term investments	$	89,902	$	89,906	$	139	$	139
Total	$	1,376,011	$	1,376,090	$	1,260,981	$	1,260,983