Investments - Summary of Available-for-Sale Debt Securities and Equity Securities (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Investments, Debt and Equity Securities [Abstract]
Proceeds from sales and maturities (fair value)	$ 52,633	$ 42,513
Proceeds from sales of equity securities	1,576	0
Gross realized gains on sale of securities	122	346
Equity securities, FV-NI, Realized Gain	343	0
Gross realized losses on sale of securities	(324)	(47)
Equity securities, FV-NI, Realized Loss	0	0
Realized gains on sales of investment real estate	$ 401	$ 0