Pensions and Other Postretirement Benefit Plans (Schedule of Pension Plans with Projected Benefit Obligation in Excess of Plan Assets and for Pension Plans with an Accumulated Benefit Obligation in Excess of Plan Assets) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Projected benefit obligation exceeds plan assets
Projected benefit obligation	$ 376,595	$ 341,870
Fair value of plan assets	267,594	227,784
Accumulated benefit obligation exceeds plan assets
Projected benefit obligation	376,595	341,870
Accumulated benefit obligation	363,228	325,602
Fair value of plan assets	$ 267,594	$ 227,784