Stockholders' Equity - Reclassifications from accumulated other comprehensive income and included in net income (Details) - Reclassifications from accumulated other comprehensive income (loss) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Reclassifications included in net income:
Pre-tax	$ 228	$ 333
Tax expense	(56)	(82)
Net of tax	172	251
Gains (losses) on available for sale debt securities | Investment and other income (loss)
Reclassifications included in net income:
Pre-tax	213	266
Tax expense	(52)	(64)
Net of tax	161	202
Postretirement benefits unrealized gains (losses) | Compensation and benefits
Reclassifications included in net income:
Pre-tax	15	67
Tax expense	(4)	(18)
Net of tax	$ 11	$ 49