Benefit Plans Regulatory Asset (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Defined Benefit Plan Disclosure [Line Items]
Regulatory asset	$ 88,218	$ 134,377
Postretirement pensions and other medical benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Funded status of obligation	44,322	74,222
Accrued benefit cost	(7,030)	(6,904)
Amount to be recovered in future rates	37,292	67,318
Tax gross-up	25,657	46,315
Regulatory asset	$ 62,949	$ 113,633