Stockholders' Equity - Reclassifications from accumulated other comprehensive income (loss) and included in net income (Details) - Reclassifications from accumulated other comprehensive income - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Reclassifications included in net income:
Pre-tax	$ 251	$ 233	$ 862	$ 605
Tax (expense) benefit	(60)	(56)	(209)	(144)
Net of tax	191	177	653	461
Gains (losses) on available for sale debt securities | Investment and other income (loss)
Reclassifications included in net income:
Pre-tax	184	109	661	234
Tax (expense) benefit	(44)	(26)	(159)	(56)
Net of tax	140	83	502	178
Postretirement benefits unrealized gains (losses) | Compensation and benefits
Reclassifications included in net income:
Pre-tax	67	124	201	371
Tax (expense) benefit	(16)	(30)	(50)	(88)
Net of tax	$ 51	$ 94	$ 151	$ 283