Defined Pension Plans (Details) (Supplemental Employee Retirement Plans, Defined Benefit [Member], USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012
Scenario, Forecast [Member]
Service cost - benefits earned during the year	$ 3,519
Interest cost on projected benefit obligation	2,821
Expected return on plan assets	(4,472)
Net amortization and deferral	1,849
Net periodic pension cost	3,717
Scenario, Actual [Member]
Service cost - benefits earned during the year	2,799
Interest cost on projected benefit obligation	2,570
Expected return on plan assets	(3,967)
Net amortization and deferral	1,473
Net periodic pension cost	$ 2,875