Pension Benefit and Retirement Health and Life Insurance Benefits (Amounts Recognized in Balance Sheet) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Pension Benefits
Defined Benefit Plan, Amounts Recognized in Balance Sheet [Abstract]
Noncurrent assets	$ 1,273	$ 404
Current liabilities	(1)	(34)
Noncurrent liabilities	(12,624)	(17,652)
Net amount recognized at end of year	(11,352)	(17,282)
Pension and Other Postretirement Benefit Plans, Accumulated Other Comprehensive Income (Loss), before Tax [Abstract]
Net actuarial (loss) gain	(62,972)	(62,053)
Prior service benefit	0	0
Net amount recognized at end of year	(62,972)	(62,053)
Retirement Health and Life Insurance Benefits
Defined Benefit Plan, Amounts Recognized in Balance Sheet [Abstract]
Noncurrent assets	0	0
Current liabilities	(537)	(1,071)
Noncurrent liabilities	(2,185)	(8,768)
Net amount recognized at end of year	(2,722)	(9,839)
Pension and Other Postretirement Benefit Plans, Accumulated Other Comprehensive Income (Loss), before Tax [Abstract]
Net actuarial (loss) gain	643	(707)
Prior service benefit	5,368	0
Net amount recognized at end of year	$ 6,011	$ (707)