Employee Benefit Plans (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended	9 Months Ended		12 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Jun. 30, 2012	Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2011
Pension benefits
Components of net periodic benefit costs:
Interest cost	$ 148	$ 180		$ 452	$ 553
Expected return on plan assets	(182)	(254)		(574)	(810)
Amortization of net loss	41	19		120	49
Settlement of benefit obligation	0	408		353	408
Net periodic benefit cost	7	353		351	200
Projected benefit obligation:
Beginning balance	16,031		16,505	16,505
Ending balance, before settlements			16,681
Impact of settlements	0		(650)
Ending balance, after settlements			16,031			16,505
Fair value of plan assets:
Beginning balance	10,166		10,409	10,409
Ending balance, before settlements			10,816
Impact of settlements			(650)
Ending balance, after settlements			10,166			10,409
Funded status, beginning balance	(5,865)		(6,096)	(6,096)
Funded status, ending balance			(5,865)			(6,096)
Gross unrealized loss:
Beginning balance	8,704		9,280	9,280
Ending balance, before settlements			9,057
Impact of settlements			(353)
Ending balance, after settlements			8,704			9,280
Assumptions:
Discount rate			4.00%			4.00%
Expected return on plan assets			7.50%			7.50%
Postretirement benefits
Components of net periodic benefit costs:
Interest cost	2	3		7	9
Expected return on plan assets	0	0		0	0
Amortization of net loss	0	(3)		(1)	(7)
Settlement of benefit obligation	0	0		0	0
Net periodic benefit cost	$ 2	$ 0		$ 6	$ 2
Postretirement benefits | Employees hired before January 1, 2003
Defined Benefit Plan Disclosure [Line Items]
Contribution per eligible employee, coverage basis, consecutive period of highest average monthly compensation				5 years
Contribution per eligible employee, coverage basis, lastest service period				10 years
Postretirement benefits | Employees hired on or after January 1, 2003
Defined Benefit Plan Disclosure [Line Items]
Percentage of annual contribution per eligible employee				2.00%
Postretirement health benefits | Employees retired before January 1, 1993
Defined Benefit Plan Disclosure [Line Items]
Maximum coverage per eligible retiree				100.00%