Summary of Significant Accounting Policies and Select Balance Sheet Information - Amortized Cost and Fair Value of Investments by Contractual Maturity (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013
Amortized cost
Debt securities due within one year	$ 10,200
Debt securities due within one to five years	22,754
Debt securities due within five years or more	9,568
Total	42,522
Fair value
Debt securities due within one year	10,212
Debt securities due within one to five years	22,782
Debt securities due within five years or more	9,615
Total	$ 42,609