Qualified Employee Benefit Plans - Net (Benefit) Expense Under the Retirement Plan (Details) - Retirement Plan [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Interest cost on projected benefit obligations	$ 4,972	$ 4,816	$ 4,895
Expected return on plan assets	(5,407)	(6,176)	(6,493)
Amortization of prior service cost	24	0	0
Recognized actuarial loss	959	979	490
Net pension (benefit) expense	$ 548	$ (381)	$ (1,108)