Fair Value Measurements - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Fair Value Disclosures [Abstract]
Unrealized (loss) gain on available-for-sale marketable securities, net of taxes	$ (679)	$ 1,156	$ (862)
Proceeds from available for sale municipal bonds	9,000	28,500	28,100
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Realized (loss) gain on sales of available-for-sale securities	$ (200)		$ (200)
Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Realized (loss) gain on sales of available-for-sale securities		$ (100)