FAIR VALUE MEASUREMENTS (Tables)

3 Months Ended

Mar. 31, 2013

Fair Value Disclosures [Abstract]

Financial assets measured at fair value on a recurring basis

The following table presents the fair value hierarchy for the Company’s financial assets measured at fair value on a recurring basis at March 31, 2013 and December 31, 2012 (in thousands): 

			Quoted Prices in Active Markets for Identical Assets		Significant Other Observable Inputs		Significant Unobservable Inputs
At March 31, 2013	Total		Level 1		Level 2		Level 3
Cash and cash equivalents	$	1,531,678	$	1,398,584	$	133,094	$	—
State and municipal bonds	1,186,935		—		1,186,935		—
U.S. Treasury securities	115,024		115,024		—		—
Government-sponsored enterprise securities	79,285		—		79,285		—
Residential mortgage-backed securities	337,198		—		337,198		—
Commercial mortgage-backed securities	33,892		—		33,892		—
Asset-backed securities	22,572		—		22,572		—
Corporate debt and other securities	1,035,012		—		1,035,012		—
Total	$	4,341,596	$	1,513,608	$	2,827,988	$	—

			Quoted Prices in Active Markets for Identical Assets		Significant Other Observable Inputs		Significant Unobservable Inputs
At December 31, 2012	Total		Level 1		Level 2		Level 3
Cash and cash equivalents	$	1,399,162	$	1,218,046	$	181,116	$	—
State and municipal bonds	1,253,789		—		1,253,789		—
U.S. Treasury securities	78,931		78,931		—		—
Government-sponsored enterprise securities	73,532		—		73,532		—
Residential mortgage-backed securities	312,641		—		312,641		—
Commercial mortgage-backed securities	21,590		—		21,590		—
Asset-backed securities	23,626		—		23,626		—
Corporate debt and other securities	991,610		—		991,610		—
Total	$	4,154,881	$	1,296,977	$	2,857,904	$	—