Annual report pursuant to Section 13 and 15(d)

Selected Balance Sheet Data - Schedule of Other Assets (Parenthetical) (Detail)

v2.4.1.9
Selected Balance Sheet Data - Schedule of Other Assets (Parenthetical) (Detail) (USD $)
 12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Other Assets [Line Items]      
Allowance of doubtful accounts $ 193,000us-gaap_AllowanceForDoubtfulAccountsReceivable $ 223,000us-gaap_AllowanceForDoubtfulAccountsReceivable  
Provision for bad debt expense 29,000us-gaap_ProvisionForDoubtfulAccounts 207,000us-gaap_ProvisionForDoubtfulAccounts 97,000us-gaap_ProvisionForDoubtfulAccounts
Write-off receivables $ 59,000us-gaap_AllowanceForDoubtfulAccountsReceivableWriteOffs $ 152,000us-gaap_AllowanceForDoubtfulAccountsReceivableWriteOffs $ 173,000us-gaap_AllowanceForDoubtfulAccountsReceivableWriteOffs
Weighted average interest rate for notes receivable 2.80%us-gaap_TimeSharingTransactionsWeightedAverageOfStatedInterestRatesForNotesReceivable1 2.20%us-gaap_TimeSharingTransactionsWeightedAverageOfStatedInterestRatesForNotesReceivable1  
Minimum [Member]      
Other Assets [Line Items]      
Notes receivable due period 1 year    
Maximum [Member]      
Other Assets [Line Items]      
Notes receivable due period 5 years