Employee Benefit Plans (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Defined Benefit Postretirement Health Coverage [Member] | Employees Retired before January 1, 1993 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Defined Benefit Plan, Maximum Coverage per Retiree	100.00%
Pension Plans, Defined Benefit [Member]
Components of net periodic benefit costs:
Interest cost	$ 133	$ 152
Expected return on plan assets	(165)	(196)
Defined Benefit Plan, Amortization of Net Gains (Losses)	52	39
Net periodic benefit cost	20	(5)
Other Postretirement Benefit Plans, Defined Benefit [Member]
Components of net periodic benefit costs:
Interest cost	2	2
Defined Benefit Plan, Amortization of Net Gains (Losses)	0	(2)
Net periodic benefit cost	$ 2	$ 0
Other Postretirement Benefit Plans, Defined Benefit [Member] | Employees Hired before January 1, 2003 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Defined Benefit Plan, Contribution Per Employee, Coverage Basis, Consecutive Period of Highest Average Monthly Compensation	5 years
Defined Benefit Plan, Contribution Per Employee, Coverage Basis, Lastest Service Period	10 years
Other Postretirement Benefit Plans, Defined Benefit [Member] | Employees Hired on or after January 1, 2003 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Defined Benefit Plan, Annual Contribution Per Employee, Percent	2.00%