Financial Instruments - Summary of Bond Activity (Detail) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
Derivative Instruments And Hedging Activities Disclosure [Abstract]
Fair value at beginning of period	$ 60,659	$ 56,556
Purchases	3,447	27,216
Sales	(13,768)	(1,686)
Maturities and calls	(3,350)	(22,272)
Change in bond premium	(343)	(460)
Fair market value adjustment	(797)	1,305
Fair value at end of period	$ 45,848	$ 60,659