Available for Sale Debt Securities by Original Contractual Maturity (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
One year or less, amortized cost	$ 85,049	$ 27,752
Marketable equity securities	0	0
Greater than one year and less than five years, amortized cost		5,705
Amortized Cost	85,049	33,457
One year or less, fair value	85,000	27,727
Marketable equity securities	11,163
Greater than one year and less than five years, fair value		5,699
Total available-for-sale securities fair value	$ 96,163	$ 33,426