Consolidated Statements of Comprehensive Income (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Statement of Comprehensive Income [Abstract]
Net unrealized gains (losses) on securities arising during the period, taxes	$ 1,541	$ (3,856)	$ 9,037
Less: reclassification adjustment for net realized gains included in net income, taxes	0	1,132	488
Less: reclassification adjustment to net income, net of tax benefits of $150, $150 and $150 for 2015, 2014 and 2013, respectively	150	150	150
Net gains (losses) arising during the period, tax benefits	3,753	(149,364)	142,478
Less: amortization of net loss, prior service gain and transition obligation included in net periodic benefit cost, tax benefits	14,344	7,245	14,870
Less: reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of (taxes) benefits of ($132,373), $141,777 and ($48,299) for 2015, 2014 and 2013, respectively	$ 16,011	$ (132,373)	$ 141,777