Cash, Cash Equivalents, and Investments - Additional Information (Detail)	9 Months Ended
	Sep. 30, 2013
Cash and Cash Equivalents [Line Items]
Initial maturities period of cash and cash equivalents	3 months
Maturities period of Long-term investments and securities	1 year
Maximum [Member]
Cash and Cash Equivalents [Line Items]
Maturities period of Short-term investments and securities	1 year