Summary of Financial Assets Measured at Fair Value on Recurring Basis (Detail) (Fair Value, Measurements, Recurring [Member], USD $) In Thousands, unless otherwise specified	Sep. 30, 2013
Assets:
Fair value measurement disclosure	$ 40,652
Fair Value, Inputs, Level 1 [Member]
Assets:
Fair value measurement disclosure	40,652
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	27,024
U.S. Treasury bills and money market funds | Fair Value, Inputs, Level 1 [Member]
Assets:
Fair value measurement disclosure	27,024
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	13,082
Operating cash | Fair Value, Inputs, Level 1 [Member]
Assets:
Fair value measurement disclosure	13,082
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