Fair Value Measurements - Assets Measured at Fair Value on Recurring Basis (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Estimated Fair Value	$ 5,675	$ 5,651
Failed Auction Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Estimated Fair Value	4,964	4,825
Recurring [Member] | Short-Term Brokered Certificates of Deposit [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Estimated Fair Value	541	463
Recurring [Member] | Failed Auction Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Estimated Fair Value	4,964	4,825
Recurring [Member] | Long-Term Brokered Certificates of Deposit [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Estimated Fair Value	170	363
Recurring [Member] | Money Market Funds [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Cash Equivalents	11,861	12,407
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	11,861	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	541	463
Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | Long-Term Brokered Certificates of Deposit [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Estimated Fair Value	170	363
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	$ 4,964	$ 4,825