Current Expected Credit Losses - Available-for-Sale Debt Securities in Unrealized Loss Position (Detail) - USD ($) $ in Thousands	Mar. 31, 2020	Jan. 01, 2020
Schedule of Available-for-sale Securities [Line Items]
Continuous Unrealized Loss Position for Less than 12 Months, Fair Value	$ 10,886	$ 8,594
Continuous Unrealized Loss Position for Less than 12 Months, Unrealized Losses	(231)	(18)
Continuous Unrealized Loss Position for 12 Months or Greater, Fair Value		136
Continuous Unrealized Loss Position for 12 Months or Greater, Unrealized Losses		(2)
Total Fair Value	10,886	8,730
Total Unrealized Losses	(231)	(20)
Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Continuous Unrealized Loss Position for Less than 12 Months, Fair Value	4,166	203
Continuous Unrealized Loss Position for Less than 12 Months, Unrealized Losses	(87)
Total Fair Value	4,166	203
Total Unrealized Losses	(87)
Municipal Fixed-Rate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Continuous Unrealized Loss Position for Less than 12 Months, Fair Value		930
Total Fair Value		930
Asset-Backed Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Continuous Unrealized Loss Position for Less than 12 Months, Fair Value	3,901	797
Continuous Unrealized Loss Position for Less than 12 Months, Unrealized Losses	(76)	(3)
Total Fair Value	3,901	797
Total Unrealized Losses	(76)	(3)
Mortgage/Agency-Backed Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Continuous Unrealized Loss Position for Less than 12 Months, Fair Value	1,577	2,594
Continuous Unrealized Loss Position for Less than 12 Months, Unrealized Losses	(62)	(6)
Continuous Unrealized Loss Position for 12 Months or Greater, Fair Value		136
Continuous Unrealized Loss Position for 12 Months or Greater, Unrealized Losses		(2)
Total Fair Value	1,577	2,730
Total Unrealized Losses	(62)	(8)
U.S. Government Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Continuous Unrealized Loss Position for Less than 12 Months, Fair Value	1,242	4,070
Continuous Unrealized Loss Position for Less than 12 Months, Unrealized Losses	(6)	(9)
Total Fair Value	1,242	4,070
Total Unrealized Losses	$ (6)	$ (9)