Investments (Tables)

6 Months Ended

Jun. 30, 2012

Investments [Abstract]

Investing In Fixed Income Securities

Investments as of June 30, 2012 and December 31, 2011 consisted of the following (tables in thousands):

	June 30, 2012
	Cost or Amortized Cost		Unrealized Gains		Unrealized Losses			Aggregate Fair Value
U.S. Government and agency obligations	$	475,556	$	1,220	$	(73	)	$	476,703
U.S. and foreign corporate debt securities	1,488,144		2,800		(821		)	1,490,123
Foreign governments and multi-national agency obligations	39,138		14		(29		)	39,123
Municipal obligations	1,160,540		2,442		(756		)	1,162,226
Asset-backed securities	36,648		53		(10		)	36,691
Mortgage-backed securities	65,122		129		(148		)	65,103
Total investments	$	3,265,148	$	6,658	$	(1,837	)	$	3,269,969

	December 31, 2011
	Cost or Amortized Cost		Unrealized Gains		Unrealized Losses			Aggregate Fair Value
U.S. Government and agency obligations	$	516,795	$	1,842	$	(23	)	$	518,614
U.S. and foreign corporate debt securities	1,134,009		1,404		(2,036		)	1,133,377
Foreign governments and multi-national agency obligations	58,455		30		(87		)	58,398
Municipal obligations	768,282		1,396		(437		)	769,241
Asset-backed securities	27,107		2		(23		)	27,086
Mortgage-backed securities	49,778		128		(172		)	49,734
Total investments	$	2,554,426	$	4,802	$	(2,778	)	$	2,556,450

Unrealized Losses On Investments

Unrealized losses on investments as of June 30, 2012, and December 31, 2011, which have been in a net loss position for less than twelve months, were classified by investment category as follows (table in thousands):

	June 30, 2012					December 31, 2011
	Fair Value		Unrealized Losses			Fair Value		Unrealized Losses
U.S. Government and agency obligations	$	214,612	$	(73	)	$	50,604	$	(23	)
U.S. and foreign corporate debt securities	500,126		(819		)	539,228		(2,036		)
Foreign governments and multi-national agency obligations	31,175		(29		)	43,026		(87		)
Municipal obligations	407,195		(756		)	298,187		(406		)
Asset-backed securities	9,399		(10		)	20,025		(23		)
Mortgage-backed securities	38,309		(148		)	32,817		(172		)
Total	$	1,200,816	$	(1,835	)	$	983,887	$	(2,747	)

Contractual Maturities Of Investments

The contractual maturities of investments held at June 30, 2012 consisted of the following (table in thousands):

	Amortized Cost Basis		Aggregate Fair Value
Due within one year	$	1,275,888	$	1,276,571
Due after 1 year through 5 years	1,929,232		1,933,370
Due after 5 years	60,028		60,028
Total investments	$	3,265,148	$	3,269,969