Retirement Plans (Details) (Pension Plans, Defined Benefit [Member], USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 755	$ 635	$ 1,513	$ 1,271
Interest cost	600	675	1,204	1,352
Expected return on plan assets	(362)	(358)	(727)	(717)
Amortization of prior service cost	43	493	86	986
Amortization of actuarial loss	799	188	1,599	377
Defined benefit expense	$ 1,835	$ 1,633	$ 3,675	$ 3,269