Marketable Investments - Summary of Maturity Periods of the Marketable Securities (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
FY 2013, Total	$ 10,157
FY 2014, Total	29,856
FY 2015, Total	30,991
Thereafter, Total	25,049
Total short and long term	96,053	143,846
State and Municipal Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
FY 2013, Total	2,772
FY 2014, Total	4,821
FY 2015, Total	2,072
Thereafter, Total
Total short and long term	9,665	18,872
Federal Agency and Corporate Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
FY 2013, Total	7,385
FY 2014, Total	25,035
FY 2015, Total	28,919
Thereafter, Total	15,957
Total short and long term	77,296	116,004
ARS [Member]
Schedule of Available-for-sale Securities [Line Items]
FY 2013, Total
FY 2014, Total
FY 2015, Total
Thereafter, Total	9,092
Total short and long term	$ 9,092	$ 8,970