XML 57 R33.htm IDEA: XBRL DOCUMENT v2.4.0.8
Marketable Investments - Additional Information (Detail) (USD $)
In Millions, unless otherwise specified
 1 Months Ended 9 Months Ended
Sep. 30, 2013
Accumulated Net Unrealized Investment Gain (Loss) [Member]
Dec. 31, 2012
Accumulated Net Unrealized Investment Gain (Loss) [Member]
Oct. 30, 2013
ARS [Member]
Subsequent Event [Member]
Sep. 30, 2013
ARS [Member]
Level 3 [Member]
Sep. 30, 2013
Minimum [Member]
Sep. 30, 2012
Minimum [Member]
Sep. 30, 2013
Maximum [Member]
Sep. 30, 2012
Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]                
Intervals for each security         7 days   35 days  
Interest rates on securities ranged         0.10% 0.10% 0.40% 0.50%
Weighted average interest rate       1.70%        
Weighted average discount rate       4.90%        
Weighted average holding period       8 years 8 months 12 days        
Unrealized loss recorded in accumulated other comprehensive income $ 1.9 $ 2.0            
Proceeds from sale of ARS     9.1          
Loss realized on ARS     $ 1.9