Fair Value of Financial Instruments - Rollforward of Balance Sheet Amounts Within Level 3 Valuation Hierarchy (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Assets measured on recurring basis, unobservable input reconciliation, calculation [Roll Forward]
Transfers out of Level 3			$ 0
Recurring | Other investments
Assets measured on recurring basis, unobservable input reconciliation, calculation [Roll Forward]
Fair value, beginning of period	$ 40,612	$ 31,522	38,156	$ 26,422
Total realized gains included in income	456	1,264	4	2,193
Changes in unrealized gains/losses included in other comprehensive income for assets and liabilities still held at period-end	0	0	0	0
Purchases	1,095	1,777	4,822	6,965
Issuances	0	0	0	0
Settlements	(957)	(615)	(1,776)	(1,632)
Transfers out of Level 3	0	0	0	0
Fair value, end of period	41,206	33,948	41,206	33,948
Total realized gains (losses) included in income related to financial assets and liabilities still on the consolidated balance sheet at period-end	456	1,264	4	2,193
Recurring | Available-for-sale Securities
Assets measured on recurring basis, unobservable input reconciliation, calculation [Roll Forward]
Fair value, beginning of period	15,295	15,263	15,903	14,595
Total realized gains included in income	27	29	82	87
Changes in unrealized gains/losses included in other comprehensive income for assets and liabilities still held at period-end	151	574	631	1,583
Purchases	0	0	0	0
Issuances	0	0	0	0
Settlements	0	0	(1,143)	(399)
Transfers out of Level 3	0	0	0	0
Fair value, end of period	15,473	15,866	15,473	15,866
Total realized gains (losses) included in income related to financial assets and liabilities still on the consolidated balance sheet at period-end	$ 27	$ 29	$ 82	$ 87