Fair Value Measurements (Details Textual) (USD $)	12 Months Ended			1 Months Ended				12 Months Ended
	Mar. 31, 2012	Apr. 02, 2011	Mar. 31, 2012 Auction Rate Securities [Member]	Mar. 31, 2007 3.125% Debentures [Member]	Mar. 31, 2012 3.125% Debentures [Member]	Apr. 02, 2011 3.125% Debentures [Member]	Mar. 31, 2012 2.625% Debentures [Member]	Mar. 31, 2012 Available-For-Sale Securities [Member]	Mar. 31, 2012 Maximum [Member]	Mar. 31, 2012 Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Balance of student loan auction rate securities measured at fair value								$ 28,900,000
Redemption of student loan auction rate securities	5,700,000	20,200,000
Student loan auction rate securities maturity date									May 2046	December 2027
Discount rates applied for comparable or similar term student loan asset-backed securities									3.33%	2.59%
Debt Instrument [Line Items]
Interest rate of debentures	3.125%	2.625%		3.125%	3.125%		2.625%
Convertible debentures due date				Mar. 15, 2037
Fair value of debentures					877,900,000		810,800,000
Principal amount of convertible debentures				1,000,000,000	689,635,000	689,635,000
Liquidity discount represent estimate of additional return compensate for lack of liquidity of student loan auction rate securities			20.00%
Fair Value Measurements (Textual) [Abstract]
Loss included in interest and other expense asset-backed securities		580,000
Weighted average life for cash flow projected	8 years
Notional value of student loan auction securities sold during the period		$ 10,800,000
Hypothetical base point increase or decrease in any financial inputs of discounted cash flow pricing model	1.00%