Marketable Securities (Tables)

3 Months Ended

Jun. 30, 2012

Marketable Securities [Abstract]

Schedule Of Available-for-sale Securities

							Estimated
			Gross		Gross		Fair Value
	Amortized		Unrealized		Unrealized		(Net Carrying
	Cost		Gains		Losses		Amount)
Corporate debt securities	$	32,554	$	21	$	(12)	$	32,563
U.S. Treasury securities		16,762		2		(2)		16,762
Agency discount notes		17,028		4		-		17,032
Commercial paper		16,006		4		(8)		16,002
Total securities	$	82,350	$	31	$	(22)	$	82,359

							Estimated
			Gross		Gross		Fair Value
	Amortized		Unrealized		Unrealized		(Net Carrying
	Cost		Gains		Losses		Amount)
Corporate debt securities	$	48,011	$	33	$	(19)	$	48,025
U.S. Treasury securities		30,264		1		(4)		30,261
Agency discount notes		16,789		8		(1)		16,796
Commercial paper		23,719		5		(15)		23,709
Total securities	$	118,783	$	47	$	(39)	$	118,791