Proceeds From Sales and Calls of Debt Securities and Associates Gains or Losses (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2019	Mar. 31, 2018
Available-for-sale
Sales of available-for-sale debt securities		$ 304,048	$ 228,681
Gross realized gains	[1]	2,937	6
Gross realized losses	[1]	(2,716)	(288)
Held-to-maturity
Proceeds from calls of debt securities		29,945	15,465
Gross realized gains	[1]	2	54
Gross realized losses	[1]	$ (10)	$ (105)

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