Investments and Fair Value Disclosures - Additional Information (Detail)	3 Months Ended
	Mar. 31, 2013
Fair Value Disclosures [Abstract]
Short-term investment maturity period description	Investments with original maturities greater than three months that mature less than one year from the consolidated balance sheet date are classified as short-term investments
Maturity period of long-term investments	Greater than one year
Short-term investment maturity term, minimum	3 months
Short-term investment maturity term, maximum	1 year