Fair Value Measurements (Tables)

6 Months Ended

Jun. 30, 2012

Fair Value Measurements [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 June 30, 2012 and December 31, 2011, were as follows:

		Fair Value Measurements at Reporting Date Using
	Fair Value	Quoted Prices in Active Markets for Identical Assets (Level 1)	Significant Other Observable Inputs (Level 2)	Significant Unobservable Inputs (Level 3)
At June 30, 2012
Unrestricted
Available-for-sale marketable securities:
U.S. government obligations	$351,788		$351,788
U.S. government guaranteed corporate bonds	50,654		50,654
Municipal bonds	12,386		12,386
Mortgage-backed securities	117		117
Equity security	2,455	$2,455
	417,400	2,455	414,945
Restricted
Available-for-sale marketable securities:
U.S. government obligations	8,044		8,044
	$425,444	$2,455	$422,989

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