Fair Value - Additional Information (Detail)	9 Months Ended
	Sep. 30, 2013
Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Period of Investment	2 years
Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Period of Investment	5 years