Accumulated Other Comprehensive Income (Loss) Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Mar. 31, 2018	Dec. 31, 2017		Mar. 31, 2017	Dec. 31, 2016
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive (loss) income	$ (986)	$ (306)	$ (986)	$ (306)	$ (888)	$ 1,732	[1]	$ (2,574)	$ (3,262)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	(32)	2,325	(2,096)	2,976
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	(66)	(57)	(622)	(20)
Other Comprehensive Income (Loss), Net of Tax	(98)	2,268	(2,718)	2,956
Accumulated Defined Benefit Plans Adjustment, Net Gain (Loss) Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive (loss) income	398	219	398	219	398	398		0	0
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	0	219	0	219
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	0	0	0	0
Other Comprehensive Income (Loss), Net of Tax	0	219	0	219
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive (loss) income	(472)	(2,238)	(472)	(2,238)	(849)	(1,564)		(2,408)	(2,905)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	377	170	1,092	667
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	0	0	0	0
Other Comprehensive Income (Loss), Net of Tax	377	170	1,092	667
Accumulated Net Investment Gain (Loss) Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive (loss) income	(912)	1,713	(912)	1,713	$ (437)	$ 2,898		$ (166)	$ (357)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	(409)	1,936	(3,188)	2,090
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	(66)	(57)	(622)	(20)
Other Comprehensive Income (Loss), Net of Tax	$ (475)	$ 1,879	$ (3,810)	$ 2,070

[1] Derived from audited consolidated financial statements