Fair Value Measurements (Tables)

9 Months Ended

Sep. 30, 2011

Fair Value Measurements

Assets And Liabilities Subject To Fair Value Measurements On Recurring Basis

	Fair Value as of September 30, 2011
	Level 1		Level 2		Level 3		Total
Cash and cash equivalents	$	37,660	$	—	$	—	$	37,660
Corporate debt securities	$	—	$	329,662	$	—	$	329,662
Residential mortgage-backed securities		—		91,830		—		91,830
Government-sponsored enterprise securities		—		15,313		—		15,313
Asset-backed securities		—		65,332		—		65,332
Marketable securities	$	—	$	502,137	$	—	$	502,137
Money market funds	$	8,844	$	—	$	—	$	8,844
U.S. Treasury securities		1,305		—		—		1,305
Corporate debt securities		—		50,284		—		50,284
Residential mortgage-backed securities		—		7,801		—		7,801
Government-sponsored enterprise securities		—		8,560		—		8,560
Asset-backed securities		—		3,127		—		3,127
Restricted investments	$	10,149	$	69,772	$	—	$	79,921