Debt Securities - Proceeds From Sales and Calls of Debt Securities and Associates Gains or Losses (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Available-for-sale
Proceeds from sales and calls of debt securities		$ 69,304	$ 401,701	$ 184,088	$ 878,072
Gross realized gains	[1]	102	14,329	1,206	18,613
Gross realized losses	[1]	(78)	(518)	(192)	(4,447)
Held-to-maturity
Proceeds from calls of debt securities		9,280	16,365	29,530	48,940
Gross realized gains	[1]	0	0	1	2
Gross realized losses	[1]	$ 0	$ 0	$ 0	$ (10)

[1] The gain or loss on the sale or call of each debt security is determined by the specific identification method.