Employee Post-Retirement Benefits (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Components of net periodic benefit cost
Service cost	$ 67	$ 150	$ 134	$ 300
Interest cost	120	188	240	376
Expected return on plan assets	0	0	0	0
Amortization of transition obligation	0	15	0	30
Amortization of prior service credits	(236)	(19)	(472)	(38)
Recognized actuarial loss	120	135	240	270
Net periodic benefit cost	$ 71	$ 469	$ 142	$ 938