Marketable Securities - Summary of Available-for-sale Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Marketable Securities with unrecognized gains	$ 135
Cost
Debt Securities, Available-for-sale [Line Items]
Total Available-for-sale Securities	34,108	$ 39,033
Cost | Certificates of deposit | Level 1
Debt Securities, Available-for-sale [Line Items]
Marketable Securities with unrecognized losses for less than 12 months	251	251
Marketable Securities with unrecognized losses for more than 12 months	0	0
Marketable Securities with unrecognized gains	1,799	1,799
Total Available-for-sale Securities	2,050	2,050
Cost | U.S. Treasury and agency notes | Level 2
Debt Securities, Available-for-sale [Line Items]
Marketable Securities with unrecognized losses for less than 12 months	0	6,485
Marketable Securities with unrecognized losses for more than 12 months	0	0
Marketable Securities with unrecognized gains	18,252	14,413
Total Available-for-sale Securities	18,252	20,898
Cost | Corporate notes | Level 2
Debt Securities, Available-for-sale [Line Items]
Marketable Securities with unrecognized losses for less than 12 months	10,455	1,004
Marketable Securities with unrecognized losses for more than 12 months	0	0
Marketable Securities with unrecognized gains	1,350	13,082
Total Available-for-sale Securities	11,805	14,086
Cost | Municipal notes | Level 2
Debt Securities, Available-for-sale [Line Items]
Marketable Securities with unrecognized losses for less than 12 months	0	0
Marketable Securities with unrecognized losses for more than 12 months	0	0
Marketable Securities with unrecognized gains	2,001	1,999
Total Available-for-sale Securities	2,001	1,999
Fair Value
Debt Securities, Available-for-sale [Line Items]
Total Available-for-sale Securities	34,228	39,084
Fair Value | Certificates of deposit | Level 1
Debt Securities, Available-for-sale [Line Items]
Marketable Securities with unrecognized losses for less than 12 months	250	250
Marketable Securities with unrecognized losses for more than 12 months	0	0
Marketable Securities with unrecognized gains	1,812	1,806
Total Available-for-sale Securities	2,062	2,056
Fair Value | U.S. Treasury and agency notes | Level 2
Debt Securities, Available-for-sale [Line Items]
Marketable Securities with unrecognized losses for less than 12 months	0	6,479
Marketable Securities with unrecognized losses for more than 12 months	0	0
Marketable Securities with unrecognized gains	18,365	14,434
Total Available-for-sale Securities	18,365	20,913
Fair Value | Corporate notes | Level 2
Debt Securities, Available-for-sale [Line Items]
Marketable Securities with unrecognized losses for less than 12 months	10,441	1,002
Marketable Securities with unrecognized losses for more than 12 months	0	0
Marketable Securities with unrecognized gains	1,353	13,106
Total Available-for-sale Securities	11,794	14,108
Fair Value | Municipal notes | Level 2
Debt Securities, Available-for-sale [Line Items]
Marketable Securities with unrecognized losses for less than 12 months	0	0
Marketable Securities with unrecognized losses for more than 12 months	0	0
Marketable Securities with unrecognized gains	2,007	2,007
Total Available-for-sale Securities	$ 2,007	$ 2,007