Employee Benefit Plans (Changes in Fair Value of Plan Assets and Plan Benefit Obligations and Funded Status of Plan) (Details) - Employee Pension Plans [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Change in Fair Value of Plan Assets
Balance at beginning of year	$ 66,057	$ 72,296
Actual return on plan assets	9,224	(1,909)
Company contribution	2,838	2,025
Benefit payments	(6,578)	(6,355)
Balance at end of year	71,541	66,057	$ 72,296
Change in Benefit Obligations
Balance at beginning of year	103,681	105,942
Interest cost	3,919	4,153	4,055
Service cost	850	600
Assumption change (gain) loss	3,854	308
Actuarial (gain) loss	492	(967)
Benefit payments	(6,578)	(6,355)
Balance at end of year	$ 106,218	$ 103,681	$ 105,942