Retirement Plans (Narrative) (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Defined Benefit Plan Disclosure [Line Items]
Pension contributions	$ 25,000,000	$ 27,500,000
Expected long-term rate of return on plan assets (in hundredths)	7.50%	7.50%
Contribution percentage to defined contribution plan (in hundredths)	101.00%
Pension plan defined benefit plan cost increase limit percentage (in hundredths)	4.00%
Aggregate contributions to the plans	22,427,000	13,793,000	11,614,000
Seafarers Pension Trust [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension contributions	$ 107,000
Contribution percentage to defined contribution plan (in hundredths)	100.00%
Maximum contribution limit (in hundredths)	5.00%