Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016	Dec. 31, 2015
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Income (Loss), Net of Tax	$ (1,397)	$ (3,294)	$ (1,484)	$ (2,794)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	87	(500)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	0	0
Other comprehensive income (loss), net of Tax	87	(500)	1,310
AOCI Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), net of Tax	87		1,310
Pension and Other Postretirement Plans Costs [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Income (Loss), Net of Tax	(1,498)	(2,984)	(1,493)	(2,842)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	(5)	(142)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	0	0
Other comprehensive income (loss), net of Tax	(5)	(142)
Interest Rate Swap [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Income (Loss), Net of Tax	101	(310)	$ 9	$ 48
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	92	(358)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	0	0
Other comprehensive income (loss), net of Tax	$ 92	$ (358)