Employee Benefits Plans (Details) - Components of net periodic benefit cost and other amounts recognized in other comprehensive income (loss) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Net periodic benefit cost:
Amortization of net loss (gain)		$ (762)	$ 681
Pension Plan [Member]
Net periodic benefit cost:
Interest cost	263	231	292
Amortization of net loss (gain)	84	111	69
Amortization of prior service cost
Net periodic benefit cost (income)	347	342	361
Other changes in plan assets and benefit obligations recognized in other comprehensive income (loss):
Net loss (gain)	1,012	(477)	747
Amortization of net (loss) gain	(84)	(111)	(69)
Amortization of prior service cost
Total recognized in other comprehensive income (loss)	928	(588)	678
Total recognized in net periodic benefit cost and other comprehensive income (loss)	1,275	(246)	1,039
Other Postretirement Benefit Plan [Member]
Net periodic benefit cost:
Interest cost	34	31	49
Amortization of net loss (gain)	(14)		11
Amortization of prior service cost	(154)	(167)	(177)
Net periodic benefit cost (income)	(134)	(136)	(117)
Other changes in plan assets and benefit obligations recognized in other comprehensive income (loss):
Net loss (gain)	1	(285)	(66)
Amortization of net (loss) gain	14		(11)
Amortization of prior service cost	154	167	177
Total recognized in other comprehensive income (loss)	169	(118)	100
Total recognized in net periodic benefit cost and other comprehensive income (loss)	$ 35	$ (254)	$ (17)