Defined Pension Plans (Details) (Supplemental Employee Retirement Plans, Defined Benefit [Member], USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011
Scenario, Forecast [Member]
Service cost - benefits earned during the year	$ 2,688
Interest cost on projected benefit obligation	2,532
Expected return on plan assets	(3,968)
Net amortization and deferral	1,396
Net periodic pension cost	2,648
Scenario, Actual [Member]
Service cost - benefits earned during the year	2,073
Interest cost on projected benefit obligation	2,423
Expected return on plan assets	(3,314)
Net amortization and deferral	603
Net periodic pension cost	$ 1,785