Consolidated Statements of Comprehensive Income (Parenthetical) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Statement of Other Comprehensive Income [Abstract]
Net unrealized gains (losses) on securities arising during the period, taxes	$ 1,049	$ (689)	$ 7,081	$ (1,261)
Less: reclassification adjustment for net realized gains included in net income, taxes	0	0	488	53
Less: reclassification adjustment to net income, tax benefits	37	37	112	112
Less: amortization of transition obligation, prior service credit and net losses recognized during the period in net periodic benefit cost, tax benefits	3,697	2,443	11,173	7,321
Less: reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, taxes	$ 3,284	$ 2,129	$ 9,852	$ 6,386