Consolidated Statements of Comprehensive Income (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Net income for common stock	$ 47,706	$ 48,404	$ 124,822	$ 104,005
Net unrealized gains on securities:
Net unrealized gains on securities arising during the period, net of taxes of $689 and $1,917 for the three months ended September 30, 2012 and 2011 and $1,261 and $4,258 for the nine months ended September 30, 2012 and 2011, respectively	1,043	3,013	1,910	6,448
Less: reclassification adjustment for net realized gains included in net income, net of taxes of nil and $146 for the three months ended September 30, 2012 and 2011 and $53 and $148 for the nine months ended September 30, 2012 and 2011, respectively		(221)	(81)	(224)
Derivatives qualified as cash flow hedges:
Net unrealized holding losses arising during the period, net of taxes (benefits) of $5 and $(4) for the three and nine months ended September 30, 2011, respectively		(5)		(8)
Less: reclassification adjustment to net income, net of tax benefits of $37 and $37 for the three months ended September 30, 2012 and 2011 and $112 and $78 for the nine months ended September 30, 2012 and 2011, respectively	59	58	177	122
Retirement benefit plans:
Less: amortization of net loss, prior service gain and transition obligation included in net periodic benefit cost, net of tax benefits of $2,443 and $1,405 for the three months ended September 30, 2012 and 2011 and $7,321 and $3,513 for the nine months ended September 30, 2012 and 2011, respectively	3,826	2,068	11,467	5,556
Less: reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of taxes of $2,129 and $1,074 for the three months ended September 30, 2012 and 2011 and $6,386 and $3,875 for the nine months ended September 30, 2012 and 2011, respectively	(3,342)	(1,732)	(10,026)	(6,084)
Other comprehensive income, net of taxes	1,586	3,181	3,447	5,810
Comprehensive income attributable to common shareholders	$ 49,292	$ 51,585	$ 128,269	$ 109,815