Stockholders' Equity - Reclassifications from accumulated other comprehensive income and included in net income (Details) - Reclassifications from accumulated other comprehensive income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Reclassifications included in net income:
Pre-tax	$ 1,122	$ 729
Tax expense	(271)	(172)
Net of tax	851	557
Gains (losses) on available for sale debt securities | Investment and other income (loss)
Reclassifications included in net income:
Pre-tax	853	234
Tax expense	(205)	(56)
Net of tax	648	178
Postretirement benefits unrealized gains (losses) | Compensation and benefits
Reclassifications included in net income:
Pre-tax	269	495
Tax expense	(66)	(116)
Net of tax	$ 203	$ 379