Stock Based Compensation - Additional Information (Detail) (USD $)	1 Months Ended					12 Months Ended							1 Months Ended	12 Months Ended			1 Months Ended
	Jul. 31, 2012	Jan. 31, 2012	Jul. 31, 2011	Jan. 31, 2011	Jul. 31, 2010	Dec. 31, 2012	Jun. 30, 2012	Mar. 31, 2012	Jun. 30, 2011	Mar. 31, 2011	Jun. 30, 2010	Mar. 31, 2010	Jan. 31, 2013 Subsequent Event	Dec. 31, 2012 Stock Options	Dec. 31, 2012 Restricted Stock Units Employees	Dec. 31, 2012 Restricted Stock Units Director	May 31, 2009 Twenty Zero Six Incentive Compensation Plan	May 31, 2009 1996 Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award
Employee Stock Purchase Plan to increase the number of shares issuable																	10,000,000	5,000,000
Aggregate number of shares issuable																	22,000,000	25,400,000
Period of stock granted to employees and executive officers vest in equal installments														4 years	4 years	1 year
Percentage of awards vesting on the first anniversary of grant date																100.00%
Stock options term						7 years
Total unrecognized expense related to non-vested restricted stock unit awards and stock options						$ 52,100,000
Unrecognized expense related to non-vested restricted stock unit awards and stock options expected to be recognized over weighted average period, in years						2 years
Maximum percent of shares allowed to purchase						10.00%
Fair market value						$ 25,000
Maximum number of shares allowed to purchase						6,000
Percentage of common stock price paid						85.00%
Percentage of common stock price paid on last business day of the purchase period						85.00%
Common stock issued to employees	600,000	600,000	600,000	800,000	600,000								600,000
Value of common stock issued to employees per share							$ 11.91	$ 11.69	$ 11.59	$ 11.65	$ 8.12	$ 8.29