Marketable Securities (Tables)

12 Months Ended

Dec. 31, 2011

Marketable Securities [Abstract]

Marketable Securities, Based on Contractual Maturity Dates

The following tables summarize the amortized cost basis of debt securities included in marketable securities, the aggregate fair value of those securities, and gross unrealized gains and losses on those securities at December 31, 2011 and 2010.  The Company classifies its debt securities, other than mortgage-backed securities, based on their contractual maturity dates.  Maturities of mortgage-backed securities have been estimated based primarily on repayment characteristics and experience of the senior tranches that the Company holds.

	Amortized	Fair	Unrealized
At December 31, 2011	Cost Basis	Value	Gains	(Losses)	Net
Unrestricted
Maturities within one year
U.S. government obligations	$12,025	$12,067	$42		$42
U.S. government guaranteed corporate bonds	15,263	15,316	53		53
U.S. government guaranteed collateralized mortgage obligations	623	622		(1)	(1)
Municipal bonds	15,314	15,326	13	(1)	12
	43,225	43,331	108	(2)	106
Maturities after one year through five years
U.S. government obligations	272,433	272,752	400	(81)	319
Mortgage-backed securities	104	28	___	(76)	(76)
	272,537	272,780	400	(157)	243
Maturities after five years through ten years
Mortgage-backed securities	164	87	___	(77)	(77)
	315,926	316,198	508	(236)	272
Restricted
Maturities within one year
U.S. government obligations	3,347	3,357	10		10
Maturities after one year through five years
U.S. government obligations	2,572	2,583	11	___	11
	5,919	5,940	21	___	21
	$321,845	$322,138	$529	$(236)	$293

	Amortized	Fair	Unrealized
At December 31, 2010	Cost Basis	Value	Gains	(Losses)	Net
Unrestricted
Maturities within one year
U.S. government obligations	$83,635	$83,684	$54	$(5)	$49
U.S. government guaranteed corporate bonds	48,173	48,531	358		358
U.S. government guaranteed      collateralized mortgage obligations	2,027	2,131	104		104
Municipal bonds	1,597	1,603	6		6
Mortgage-backed securities	875	847	___	(28)	(28)
	136,307	136,796	522	(33)	489
Maturities after one year through five years
U.S. government obligations	352,345	350,683	64	(1,726)	(1,662)
U.S. government guaranteed corporate bonds	15,522	15,477		(45)	(45)
Mortgage-backed securities	110	38	___	(72)	(72)
	367,977	366,198	64	(1,843)	(1,779)
Maturities after five years through ten years
Mortgage-backed securities	284	243	___	(41)	(41)
	504,568	503,237	586	(1.917)	(1,331)
Restricted
Maturities within one year
U.S. government obligations	2,922	2,921		(1)	(1)
Maturities after one year through five years
U.S. government obligations	4,135	4,118	___	(17)	(17)
	7,057	7,039	___	(18)	(18)
	$511,625	$510,276	$586	$(1,935)	$(1,349)

Fair Value and Unrealized Losses of Marketable Securities

The following table shows the fair value of the Company's marketable securities that have unrealized losses and that are deemed to be only temporarily impaired, aggregated by investment category and length of time that the individual securities have been in a continuous unrealized loss position, at December 31, 2011 and 2010.  The debt securities listed at December 31, 2011, excluding mortgage-backed securities, mature at various dates through December 2014.  The mortgage-backed securities listed at December 31, 2011 mature at various dates through April 2018.

	Less than 12 Months		12 Months or Greater		Total
At December 31, 2011	Fair Value	Unrealized Loss	Fair Value	Unrealized Loss	Fair Value	Unrealized Loss
Unrestricted
U.S. government obligations	$103,529	$(81)			$103,529	$(81)
U.S. government guaranteed   collateralized mortgage   obligations	623	(1)			623	(1)
Municipal bonds	4,603	(1)			4,603	(1)
Equity security	3,019	(1,025)			3,019	(1,025)
Mortgage-backed securities	_____	____	$116	$(152)	116	(152)
	$111,774	$(1,108)	$116	$(152)	$111,890	$(1,260)
At December 31, 2010
Unrestricted
U.S. government obligations	$340,444	$(1,731)			$340,444	$(1,731)
U.S. government guaranteed   corporate bonds	19,005	(45)			19,005	(45)
Equity security	3,612	(433)			3,612	(433)
Mortgage-backed securities	_____	____	$1,128	$(141)	1,128	(141)
	363,061	(2,209)	1,128	(141)	364,189	(2,350)
Restricted
U.S. government obligations	6,154	(18)	____	____	6,154	(18)
	6,154	(18)	____	____	6,154	(18)
	$369,215	$(2,227)	$1,128	$(141)	$370,343	$(2,368)

Fair Value, Assets Measured on a Recurring Basis

The Company's assets that are measured at fair value on a recurring basis, at December 31, 2011 and 2010, 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 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
At December 31, 2010
Unrestricted
Available-for-sale marketable securities
U.S. government obligations	$434,367		$434,367
U.S. government guaranteed corporate bonds	64,008		64,008
U.S. government guaranteed collateralized mortgage obligations	2,131		2,131
Municipal bonds	1,603		1,603
Mortgage-backed securities	1,128		1,128
Equity security	3,612	$3,612	_______
	506,849	3,612	503,237
Restricted
Available-for-sale marketable securities
U.S. government obligations	7,039	_____	7,039
	$513,888	$3,612	$510,276