Cash, cash equivalents, short-term investments, and marketable securities (Tables)

9 Months Ended

Sep. 30, 2011

Cash, cash equivalents, short-term investments, and marketable securities [Abstract]

Schedule of cash, cash equivalents, short-term investments, and marketable securities

	September 30, 2011		December 31, 2010
Cash and cash equivalents:
Cash	$	17,114	$	31,795
Cash equivalents:
Commercial paper		7,998		—
Money market mutual funds		164,629		345,156
Total cash and cash equivalents		189,741		376,951
Short-term investments and marketable securities:
Short-term municipal bond fund		20,520		20,275
Commercial paper		13,971		—
Corporate notes and bonds		118,421		—
U.S. government agencies		13,154		—
Total short-term investments and marketable securities		166,066		20,275
Total cash, cash equivalents, short-term investments, and marketable securities	$	355,807	$	397,226

Schedule of Company's investments

	Amortized Cost		Gross Unrealized				Fair Value
			Gains		Losses
As of September 30, 2011:
Short-term municipal bond fund	$	20,436	$	84	$	—	$	20,520
Commercial paper		13,988		—		17		13,971
Corporate notes and bonds		118,535		70		184		118,421
U.S. government agencies		13,156		2		4		13,154
Total	$	166,115	$	156	$	205	$	166,066
As of December 31, 2010:
Short-term municipal bond fund	$	20,233	$	42	$	—	$	20,275
Total	$	20,233	$	42	$	—	$	20,275

Schedule of available-for-sale investments at contractual maturities

	Due within 1 year		Due within 2 years		Total
Short-term municipal bond fund	$	20,520	$	—	$	20,520
Commercial paper		13,971		—		13,971
Corporate notes and bonds		42,096		76,325		118,421
U.S. government agencies		—		13,154		13,154
Total	$	76,587	$	89,479	$	166,066