Defined Benefit Plans - Net Periodic Pension and Postretirement Benefit Costs (Details) (USD $)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Pension Plans, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Contributions by Employer	$ 700,000
Service costs	240,000	190,000
Interest costs	420,000	440,000
Expected return on plan assets	(520,000)	(520,000)
Amortization of net (gain)/loss	380,000	280,000
Net periodic benefit cost	520,000	390,000
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service costs	0	0
Interest costs	10,000	10,000
Expected return on plan assets	0	0
Amortization of net (gain)/loss	(10,000)	(20,000)
Net periodic benefit cost	$ 0	$ (10,000)