Cash, cash equivalents, and investments - Schedule of Company's Investments Measured at Fair Value (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014
Cash And Short Term Investments [Line Items]
Amortized Cost	$ 59,751
Total Fair Value	59,769
Corporate Bonds [Member]
Cash And Short Term Investments [Line Items]
Amortized Cost	14,692
Total Fair Value	14,684
State and Municipal Obligations [Member]
Cash And Short Term Investments [Line Items]
Amortized Cost	17,419
Total Fair Value	17,445
Cash [Member]
Cash And Short Term Investments [Line Items]
Amortized Cost	23,099
Total Fair Value	23,099
Money Market Funds [Member]
Cash And Short Term Investments [Line Items]
Amortized Cost	1,924
Total Fair Value	1,924
Certificates of Deposit [Member]
Cash And Short Term Investments [Line Items]
Amortized Cost	2,617
Total Fair Value	2,617
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Cash And Short Term Investments [Line Items]
Total Fair Value	39,715
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Corporate Bonds [Member]
Cash And Short Term Investments [Line Items]
Total Fair Value	14,692
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Cash [Member]
Cash And Short Term Investments [Line Items]
Total Fair Value	23,099
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Money Market Funds [Member]
Cash And Short Term Investments [Line Items]
Total Fair Value	1,924
Significant Other Observable Inputs (Level 2) [Member]
Cash And Short Term Investments [Line Items]
Total Fair Value	20,036
Significant Other Observable Inputs (Level 2) [Member] | State and Municipal Obligations [Member]
Cash And Short Term Investments [Line Items]
Total Fair Value	17,419
Significant Other Observable Inputs (Level 2) [Member] | Certificates of Deposit [Member]
Cash And Short Term Investments [Line Items]
Total Fair Value	$ 2,617