Fair Value Measurements - Assets Measured at Fair Value on Recurring Basis (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Estimated Fair Value	$ 5,688	$ 5,651
Failed Auction Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Estimated Fair Value	4,864	4,825
Brokered Certificates of Deposit [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Estimated Fair Value	824	826
Recurring [Member] \| Short-Term Brokered Certificates of Deposit [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Estimated Fair Value	643	463
Recurring [Member] \| Failed Auction Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Estimated Fair Value	4,864	4,825
Recurring [Member] \| Brokered Certificates of Deposit [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Estimated Fair Value	181	363
Recurring [Member] \| Money Market Funds [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Cash Equivalents	12,176	12,407
Recurring [Member] \| Quoted Prices in Active Markets (Level 1) [Member] \| Short-Term Brokered Certificates of Deposit [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Estimated Fair Value
Recurring [Member] \| Quoted Prices in Active Markets (Level 1) [Member] \| Failed Auction Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Estimated Fair Value
Recurring [Member] \| Quoted Prices in Active Markets (Level 1) [Member] \| Brokered Certificates of Deposit [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Estimated Fair Value
Recurring [Member] \| Quoted Prices in Active Markets (Level 1) [Member] \| Money Market Funds [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Cash Equivalents	12,176	12,407
Recurring [Member] \| Significant Other Observable Inputs (Level 2) [Member] \| Short-Term Brokered Certificates of Deposit [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Estimated Fair Value	643	463
Recurring [Member] \| Significant Other Observable Inputs (Level 2) [Member] \| Failed Auction Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Estimated Fair Value
Recurring [Member] \| Significant Other Observable Inputs (Level 2) [Member] \| Brokered Certificates of Deposit [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Estimated Fair Value	181	363
Recurring [Member] \| Significant Other Observable Inputs (Level 2) [Member] \| Money Market Funds [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Cash Equivalents
Recurring [Member] \| Significant Unobservable Inputs (Level 3) [Member] \| Short-Term Brokered Certificates of Deposit [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Estimated Fair Value
Recurring [Member] \| Significant Unobservable Inputs (Level 3) [Member] \| Failed Auction Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Estimated Fair Value	4,864	4,825
Recurring [Member] \| Significant Unobservable Inputs (Level 3) [Member] \| Brokered Certificates of Deposit [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Estimated Fair Value
Recurring [Member] \| Significant Unobservable Inputs (Level 3) [Member] \| Money Market Funds [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Cash Equivalents