Consolidated Statements of Comprehensive Income (unaudited) (Parenthetical) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Statement of Comprehensive Income [Abstract]
Net unrealized gains (losses) on available-for-sale investment securities arising during the period, net of tax benefits	$ (2,439)	$ 1,679	$ (161)	$ 3,343
Less: reclassification adjustment for net realized gains included in net income, net of tax benefits	0	0	0	1,132
Less: reclassification adjustment to net income, net of tax benefits	(38)	(38)	(75)	(75)
Less: amortization of prior service credit and net losses recognized during the period in net periodic benefit cost, net of tax benefits	(3,691)	(1,836)	(7,177)	(3,632)
Less: reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of tax benefits	$ (3,359)	$ (1,641)	$ (6,486)	$ (3,239)