Fair Value - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Fair Value Disclosures [Abstract]
Transfers out of Level 2 to Level 1, Assets	$ 0	$ 0	$ 24,000,000	$ 0
Transfers out of Level 1 to Level 2, Assets	$ 0	$ 0	$ 1,000,000	$ 0