Other Comprehensive Income (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Other Comprehensive Income (Loss)
Fair value adjustment to cash flow hedges, before tax	$ 0	$ (882)	$ (4,643)
Fair value adjustment to cash flow hedges, tax (expense) benefit	0	401	1,895
Fair value adjustment to cash flow hedges, net of tax	0	(481)	(2,748)
Reclassification adjustment for cash flow hedge amounts included in net earnings, before tax	11,657	19,619	16,728
Reclassification adjustment for cash flow hedge amounts included in net earnings, tax (expense) benefit	(4,506)	(8,910)	(6,826)
Reclassification adjustment for cash flow hedge amounts included in net earnings, net of tax	7,151	10,709	9,902
Adjustment for funded status of pension and postretirement benefit plans, before tax	(88,033)	5,683	(28,784)
Adjustment for funded status of pension and postretirement benefit plans, tax (expense) benefit	33,667	(2,482)	11,417
Adjustment for funded status of pension and postretirement benefit plans	(54,366)	3,201	(17,367)
Amortization of pension and postretirement plan actuarial loss and prior service cost, before tax	12,485	6,371	1,886
Amortization of pension and postretirement plan actuarial loss and prior service cost, tax (expense) benefit	(4,775)	(2,781)	(748)
Amortization of pension and postretirement plan actuarial loss and prior service cost, net of tax	7,710	3,590	1,138
Total other comprehensive income (loss), before tax	(63,891)	30,791	(14,813)
Total other comprehensive income (loss), tax (expense) benefit	24,386	(13,772)	5,738
Total other comprehensive income (loss), net of tax	$ (39,505)	$ 17,019	$ (9,075)