Retirement Plans (Details) (Pension Plans, Defined Benefit [Member], USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 758	$ 636
Interest cost	604	677
Expected return on plan assets	(365)	(359)
Amortization of prior service cost	43	493
Amortization of actuarial loss	800	189
Defined benefit expense	$ 1,840	$ 1,636