Fair Value Measurements - Additional Information (Detail)	6 Months Ended
	Jun. 30, 2016 USD ($)
Fair Value Disclosures [Abstract]
Percent of credit loss	2.20%
Rate of return required	5.00%
Estimated timeframe for auctions of securities minimum	3 years
Estimated timeframe for auctions of securities maximum	5 years
Percentage of liquidity risk premium	5.00%
Increase or decrease in the liquidity risk premium	1.00%
Increase or decrease, respectively, the fair value of the Failed Auction Securities	$ 100,000
Fair Value, Assets, Level 1 to Level 2 Transfers, Amount	$ 0