Employee Benefit Plans (Details 4) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012
Health care cost trend:
Effect on total of service and interest cost components, 1-percentage point increase	$ 6,555
Effect on total of service and interest cost components, 1-percentage point decrease	(5,153)
Effect on postretirement benefit obligation, 1-percentage point increase	97,315
Effect on postretirement benefit obligation, 1-percentage point decrease	(79,003)
Discount rate:
Effect on postretirement service and interest cost components, 1-percentage point increase	(339)
Effect on postretirement service and interest cost components, 1-percentage point decrease	356
Effect on postretirement benefit obligation, 1-percentage point increase	(82,384)
Effect on postretirement benefit obligation, 1-percentage point decrease	103,727
Effect on current year postretirement benefits expense, 1-percentage point increase	(5,085)
Effect on current year postretirement benefits expense, 1-percentage point decrease	6,258
Effect on pension service and interest cost components, 1-percentage point increase	88
Effect on pension service and interest cost components, 1-percentage point decrease	(179)
Effect on pension benefit obligation, 1-percentage point increase	(31,734)
Effect on pension benefit obligation, 1-percentage point decrease	38,655
Effect on current year pension expense, 1-percentage point increase	(2,661)
Effect on current year pension expense, 1-percentage point decrease	3,142
Expected return on plan assets:
Effect on current year pension expense, 1-percentage point increase	(2,081)
Effect on current year pension expense, 1-percentage point decrease	2,081
Rate of compensation increase:
Effect on pension service and interest cost components, 1-percentage point increase	520
Effect on pension service and interest cost components, 1-percentage point decrease	(465)
Effect on pension benefit obligation, 1-percentage point increase	4,092
Effect on pension benefit obligation, 1-percentage point decrease	(3,748)
Effect on current year pension expense, 1-percentage point increase	893
Effect on current year pension expense, 1-percentage point decrease	$ (808)