Fair Value Measurements (Tables)

9 Months Ended

Sep. 30, 2012

Fair Value Disclosures [Abstract]

Schedule of assets measured at fair value on a recurring basis

The Company’s assets that are measured at fair value on a recurring basis, at September 30, 2012 and December 31, 2011, consist of the following:

			Fair Value Measurements at Reporting Date Using
At September 30, 2012	Fair Value		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Unrestricted
Available-for-sale marketable securities:
U.S. government obligations	$	368,963			$	368,963
U.S. government guaranteed corporate bonds	57,980				57,980
Municipal bonds	26,577				26,577
Mortgage-backed securities	91				91
Equity security	2,543		$	2,543
	456,154		2,543		453,611
Restricted
Available-for-sale marketable securities:
U.S. government obligations	8,028				8,028
	$	464,182	$	2,543	$	461,639
At December 31, 2011
Unrestricted
Available-for-sale marketable securities:
U.S. government obligations	$	284,819			$	284,819
U.S. government guaranteed corporate bonds	15,316				15,316
U.S. government guaranteed collateralized mortgage obligations	622				622
Municipal bonds	15,326				15,326
Mortgage-backed securities	115				115
Equity security	3,019		$	3,019
	319,217		3,019		316,198
Restricted
Available-for-sale marketable securities:
U.S. government obligations	5,940				5,940
	$	325,157	$	3,019	$	322,138