Shareholders' Equity (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Amortization of Net Loss [Member]
Amounts recognized as a component of net periodic pension and other postretirement benefit cost:
Total before income taxes	$ (5,105)	$ (6,379)	$ (10,210)	$ (12,688)
Amortization of Prior Service Credit [Member]
Amounts recognized as a component of net periodic pension and other postretirement benefit cost:
Total before income taxes	1,241	1,126	2,482	2,241
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Amounts recognized as a component of net periodic pension and other postretirement benefit cost:
Total before income taxes	(3,864)	(5,253)	(7,728)	(10,447)
Income tax benefit	1,349	1,840	2,698	3,648
Total reclassifications for the period, net of income taxes	$ (2,515)	$ (3,413)	$ (5,030)	$ (6,799)