XML 41 R27.htm IDEA: XBRL DOCUMENT v3.19.2
Fair Value Measurements - Additional Information (Details) - USD ($)
6 Months Ended 12 Months Ended
Jun. 30, 2019
Dec. 31, 2018
Fair Value Disclosures [Abstract]    
Fair value assets transferred from level 1 to level 2 $ 0 $ 0
Fair value assets transferred from level 2 to level 1 0 0
Fair value liabilities transferred from level 1 to level 2 0 0
Fair value liabilities transferred from level 2 to level 1 0 0
Fair value assets transferred into level 3 0 0
Fair value assets transferred out of level 3 0 0
Fair value liabilities transferred into level 3 0 0
Fair value liabilities transferred out of level 3 0 0
Realized gains (loss) on sale or maturity of available-for-sale marketable securities 0 0
Reclassification out of accumulated other comprehensive loss $ 0 $ 0