Fair Value Measurement - Recurring Basis (Detail) - USD ($) $ in Thousands		Dec. 31, 2018	Dec. 31, 2017
Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds	[1]	$ 1,602	$ 1,427
Debt securities – municipal securities	[1]	2,524	1,887
Financial and Nonfinancial Liabilities, Fair Value Disclosure		0	0
Fair Value, Measurements, Recurring [Member] | Fair Value Measurements at Reporting Date Using Level 1 Inputs
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds		1,602	1,427
Debt securities – municipal securities		0	0
Fair Value, Measurements, Recurring [Member] | Fair Value Measurements at Reporting Date Using Level 2 Inputs [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds		0	0
Debt securities – municipal securities		2,524	1,887
Fair Value, Measurements, Recurring [Member] | Fair Value Measurements at Reporting Date Using Level 3 Inputs [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds		0	0
Debt securities – municipal securities		0	0
Fair Value, Measurements, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial and Nonfinancial Liabilities, Fair Value Disclosure		$ 0	$ 0

[1] The money market funds and debt securities are trading securities and are restricted to meet statutory requirements. The carrying value, included within "Other long-term assets" in the Company's consolidated balance sheets, approximates the estimated fair value.