Fair Value Measurements - Schedule Of Fair Value Of Assets (Details) - Fair value, measurements, recurring - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Fair Value Measurements [Line Items]
Assets measured at fair value	$ 23,598	$ 21,301
Mutual Funds | Investments, employee benefit plans, at fair value
Fair Value Measurements [Line Items]
Mutual funds and money market funds, fair value	21,654	19,378
Money market funds | Investments, employee benefit plans, at fair value
Fair Value Measurements [Line Items]
Mutual funds and money market funds, fair value	1,944	1,923
Level 1
Fair Value Measurements [Line Items]
Assets measured at fair value	21,654	19,378
Level 1 | Mutual Funds | Investments, employee benefit plans, at fair value
Fair Value Measurements [Line Items]
Mutual funds and money market funds, fair value	21,654	19,378
Level 1 | Money market funds | Investments, employee benefit plans, at fair value
Fair Value Measurements [Line Items]
Mutual funds and money market funds, fair value	0	0
Level 2
Fair Value Measurements [Line Items]
Assets measured at fair value	1,944	1,923
Level 2 | Mutual Funds | Investments, employee benefit plans, at fair value
Fair Value Measurements [Line Items]
Mutual funds and money market funds, fair value	0	0
Level 2 | Money market funds | Investments, employee benefit plans, at fair value
Fair Value Measurements [Line Items]
Mutual funds and money market funds, fair value	1,944	1,923
Level 3
Fair Value Measurements [Line Items]
Assets measured at fair value	0	0
Level 3 | Mutual Funds | Investments, employee benefit plans, at fair value
Fair Value Measurements [Line Items]
Mutual funds and money market funds, fair value	0	0
Level 3 | Money market funds | Investments, employee benefit plans, at fair value
Fair Value Measurements [Line Items]
Mutual funds and money market funds, fair value	$ 0	$ 0