Consolidated Statements of Comprehensive Income (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Net income for common stock	$ 38,800	$ 27,139	$ 77,116	$ 55,601
Net unrealized gains on securities:
Net unrealized gains on securities arising during the period, net of taxes of $721 and $2,755 for the three months ended June 30, 2012 and 2011 and $572 and $2,341 for the six months ended June 30, 2012 and 2011, respectively	1,093	4,061	867	3,435
Less: reclassification adjustment for net realized gains included in net income, net of taxes of $53 and $2 for the three months ended June 30, 2012 and 2011 and $53 and $2 for the six months ended June 30, 2012 and 2011, respectively	(81)	(3)	(81)	(3)
Derivatives qualified as cash flow hedges:
Net unrealized holding gains (losses) arising during the period, net of taxes of $3 and $9 for the three and six months ended June 30, 2011, respectively		6		(3)
Less: reclassification adjustment to net income, net of tax benefits of $38 and $38 for the three months ended June 30, 2012 and 2011 and $75 and $41 for the six months ended June 30, 2012 and 2011, respectively	59	59	118	64
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 $2,405 and $1,477 for the three months ended June 30, 2012 and 2011 and $4,878 and $2,108 for the six months ended June 30, 2012 and 2011, respectively	3,768	2,449	7,641	3,488
Less: reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of taxes of $2,095 and $1,370 for the three months ended June 30, 2012 and 2011 and $4,257 and $2,801 for the six months ended June 30, 2012 and 2011, respectively	(3,289)	(2,105)	(6,684)	(4,352)
Other comprehensive income, net of taxes	1,550	4,467	1,861	2,629
Comprehensive income attributable to common shareholders	$ 40,350	$ 31,606	$ 78,977	$ 58,230