Fair Value Measurements - Changes in Level 3 assets measured at fair value on a recurring basis (Details) - Available-for-sale Securities - Level 3 - Recurring basis fair value measurements - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2019	Dec. 31, 2018
Level 3 Fair Value Measurements:
Balance at beginning of year	$ 8,490	$ 9,151
Paydowns/Sales/Settlements	(5,660)	(661)
Balance at end of period	$ 2,830	$ 8,490