Short- and Long-Term Investments and Investments on Deposit for Licensure (Tables)

6 Months Ended

Jun. 30, 2011

Short- and Long-Term Investments and Investments on Deposit for Licensure [Abstract]

Reconciliation schedule of available-for-sale securities from cost basis to fair value

			Gross		Gross
	Amortized		Unrealized		Unrealized		Fair
	Cost		Holding Gains		Holding Losses		Value
Auction rate securities	$	16,750	$	—	$	1,078	$	15,672
Certificates of deposit		7,002		—		—		7,002
Commercial paper		51,268		—		6		51,262
Corporate bonds		343,337		2,917		75		346,179
Debt securities of government sponsored entities		374,866		776		198		375,444
Equity index funds		15,888		329		—		16,217
Federally insured corporate bonds		21,045		185		—		21,230
Money market funds		23,791		—		—		23,791
Municipal bonds		355,121		7,065		431		361,755
U.S. Treasury securities		34,393		105		—		34,498
Total	$	1,243,461	$	11,377	$	1,788	$	1,253,050

			Gross		Gross
	Amortized		Unrealized		Unrealized		Fair
	Cost		Holding Gains		Holding Losses		Value
Auction rate securities	$	22,650	$	—	$	1,357	$	21,293
Certificates of deposit		13,651		—		—		13,651
Commercial paper		14,797		—		4		14,793
Corporate bonds		235,775		2,327		186		237,916
Debt securities of government sponsored entities		331,893		623		465		332,051
Federally insured corporate bonds		21,097		360		3		21,454
Money market funds		20,315		—		—		20,315
Municipal bonds		301,234		1,145		1,562		300,817
U.S. Treasury securities		21,592		130		1		21,721
Total	$	983,004	$	4,585	$	3,578	$	984,011

Schedule of amortized cost and fair value of available-for-sale debt securities by contractual maturity

	Amortized		Fair
	Cost		Value
Maturing within one year	$	464,912	$	465,751
Maturing between one year and five years		515,855		519,137
Maturing between five years and ten years		178,643		183,639
Maturing in greater than ten years		68,163		68,306
Total	$	1,227,573	$	1,236,833

Net unrealized holding gain (loss) on available-for-sale securities recorded to accumulated other comprehensive income

	Three Months Ended				Six Months Ended
	June 30,				June 30,
	2011		2010		2011		2010
Net unrealized gain recorded to accumulated other comprehensive income	$	9,546	$	972	$	8,583	$	1,445

Schedule of available-for-sale securities with unrealized losses not deemed to be other-than-temporarily impaired

	Less than 12 Months						12 Months or Greater
			Gross		Total				Gross		Total
	Fair		Unrealized		Number of		Fair		Unrealized		Number of
	Value		Holding Losses		Securities		Value		Holding Losses		Securities
June 30, 2011:
Auction rate securities	$	—	$	—		—	$	15,672	$	1,078		4
Commercial paper		17,985		6		1		—		—		—
Corporate bonds		50,231		70		22		8,983		5		1
Debt securities of government sponsored entities		71,396		198		18		—		—		—
Municipal bonds		45,002		328		13		1,912		103		1
Total temporarily impaired securities	$	184,614	$	602		54	$	26,567	$	1,186		6

	Less than 12 Months						12 Months or Greater
			Gross		Total				Gross		Total
	Fair		Unrealized		Number of		Fair		Unrealized		Number of
	Value		Holding Losses		Securities		Value		Holding Losses		Securities
December 31, 2010:
Auction rate securities	$	—	$	—		—	$	21,293	$	1,357		6
Commercial paper		19,495		4		8		—		—		—
Corporate bonds		71,278		186		37		—		—		—
Debt securities of government sponsored entities		86,881		465		29		—		—		—
Federally insured corporate bond		4,036		3		1		—		—		—
Municipal bonds		160,860		1,562		64		—		—		—
U.S. Treasury securities		9,564		1		3		—		—		—
Total temporarily impaired securities	$	352,114	$	2,221		142	$	21,293	$	1,357		6