Summary of Financial Assets Measured at Fair Value on Recurring Basis (Detail) (Fair Value, Measurements, Recurring [Member], USD $) In Thousands, unless otherwise specified	Dec. 31, 2013
Assets:
Fair value measurement disclosure	$ 45,081
Fair Value, Inputs, Level 1 [Member]
Assets:
Fair value measurement disclosure	45,081
Fair Value, Inputs, Level 2 [Member]
Assets:
Fair value measurement disclosure	0
Fair Value, Inputs, Level 3 [Member]
Assets:
Fair value measurement disclosure	0
U.S. Treasury bills and money market funds
Assets:
Fair value measurement disclosure	23,026
U.S. Treasury bills and money market funds | Fair Value, Inputs, Level 1 [Member]
Assets:
Fair value measurement disclosure	23,026
U.S. Treasury bills and money market funds | Fair Value, Inputs, Level 2 [Member]
Assets:
Fair value measurement disclosure	0
U.S. Treasury bills and money market funds | Fair Value, Inputs, Level 3 [Member]
Assets:
Fair value measurement disclosure	0
Operating cash
Assets:
Fair value measurement disclosure	21,509
Operating cash | Fair Value, Inputs, Level 1 [Member]
Assets:
Fair value measurement disclosure	21,509
Operating cash | Fair Value, Inputs, Level 2 [Member]
Assets:
Fair value measurement disclosure	0
Operating cash | Fair Value, Inputs, Level 3 [Member]
Assets:
Fair value measurement disclosure	0
Restricted cash
Assets:
Fair value measurement disclosure	546
Restricted cash | Fair Value, Inputs, Level 1 [Member]
Assets:
Fair value measurement disclosure	546
Restricted cash | Fair Value, Inputs, Level 2 [Member]
Assets:
Fair value measurement disclosure	0
Restricted cash | Fair Value, Inputs, Level 3 [Member]
Assets:
Fair value measurement disclosure	$ 0