Pension Plans - Qualified Plan - Net Periodic Pension Expense (Details) - Pension Plan [Member] - Qualified Plan [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Interest cost	$ 2,829	$ 3,019	$ 3,173
Expected return on plan assets	(4,363)	(4,202)	(4,131)
Recognized net actuarial loss	750	919	1,047
Net settlement loss	1,559	1,734	1,715
Total net periodic benefit cost (credit)	$ 775	$ 1,470	$ 1,804