Fair value measurements (Tables)

12 Months Ended

Mar. 31, 2013

Fair value measurements [Abstract]

Fair value hierarchy of financial assets

The following table presents the fair value hierarchy of the Company's financial assets at March 31, 2013 and 2012:

(In thousands) Description	Fair value at March 31, 2013		Quoted prices in active markets for identical assets  (Level 1)		Significant other observable market inputs  (Level 2)		Unobservable market inputs  (Level 3)
Money market accounts	$	818,474	$	818,474
Municipal bonds and notes		46,877			$	46,877
Commercial paper		168,639		31,815		136,824
Variable rate demand notes		1,500				1,500
Auction rate securities		3,198					$	3,198
Certificates of deposit		90,268		5,981		84,287
Corporate bonds		1,509,870				1,509,870
Government agency bonds		278,804				278,804

(In thousands) Description	Fair value at March 31, 2012		Quoted prices in active markets for identical assets  (Level 1)		Significant other observable market inputs  (Level 2)		Unobservable market inputs  (Level 3)
Money market accounts	$	1,059,868	$	938,526	$	121,342
Municipal bonds and notes		69,613				69,613
Commercial paper		556,794		284,981		271,813
Variable rate demand notes		4,000				4,000
Floating rate notes		467,259		467,259
Auction rate securities		25,089					$	25,089
Certificates of deposit		215,801		87,904		127,897
Corporate bonds		568,775				568,775
Government agency bonds		152,916				152,916

Investments measured at fair value on a recurring basis using unobservable inputs

The following table presents a reconciliation of the Level 3 investments measured at fair value on a recurring basis using unobservable inputs:

(In thousands)	Year ended March 31, 2013
Balance at beginning of period	$	25,089
Sales		( 21,139	)
Unrealized loss		(752	)
Balance at end of period	$	3,198