Retirement Plans (Details) - Net benefit cost (Defined benefit plan, USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Defined benefit plan
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 1,291	$ 919
Interest cost	3,557	3,337
Expected return on plan assets	(3,028)	(1,558)
Amortization of net actuarial loss	915	373
Transfer from AOCI	3,363	0
Net benefit cost	$ 6,098	$ 3,071