Employee Benefit Plans (Rollforward of Plan Assets and Benefit Obligation) (Details) - Health Insurance Postretirement Benefit - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Change in plan assets:
Fair value of plan assets at beginning of year	$ 0	$ 0	$ 0
Employer contributions	32	31	19
Benefits paid	(32)	(31)	(19)
Fair value of plan assets at end of year	0	0	0
Change in benefit obligation:
Benefit obligation at beginning of year	1,490	1,534	1,135
Service cost	54	70	49
Interest cost	60	59	43
Estimated benefits paid	(32)	(31)	(19)
Actuarial loss (gain)	185	(142)	326
Benefit obligation at end of year	1,757	1,490	1,534
Funded status at end of year	1,757	1,490	1,534
Accumulated benefit obligation at end of year	$ 1,757	$ 1,490	$ 1,534