Qualified Employee Benefit Plans - Amounts Included in Accumulated Other Comprehensive Income (Loss) (Details) - Retirement Plan [Member] - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Unrecognized net loss from experience different from that assumed and effects of changes and assumptions	$ (43,314)	$ (46,196)
Prior service cost	(895)	0
Pension and other postretirement benefit plans, accumulated other comprehensive loss, before tax	(44,209)	(46,196)
Income tax benefit	468	567
Accumulated other comprehensive loss	$ (43,741)	$ (45,629)