Fair Value of Financial Assets and Liabilities - Additional Information (Detail) (USD $)	12 Months Ended				3 Months Ended	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2011 Foreign Sovereign Debt Securities	Dec. 31, 2011 Foreign Debt Securities	Jun. 30, 2011 VMware	Dec. 31, 2011 Variable Rate Demand Note
Percetange of foreign debt securities			9.00%
Auction rate securities that have partial guarantees by the U.S. government, market value	$ 18,300,000
Average credit rating			AA+	AA-
Percentage of Loans collateralized auction rate securities	FFELP guarantees at least 95% of the loans which collateralize the auction rate securities.
The rate used for the discount margin to determine the estimated fair value of investment in auction rate securities	2.00%	1.00%
Strategic investments held at cost included in other assets, net	159,800,000	66,400,000
Short term investment	1,786,987,000	1,256,175,000				6,600,000
Contractual maturity period	90 days	90 days
Contractual maturity year						2013
Gain on sale of strategic investment					$ 56,000,000