Consolidated Statements of Comprehensive Income (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Statement of Comprehensive Income [Abstract]
Net unrealized gains (losses) on securities arising during the period, taxes	$ (3,763)	$ (1,541)	$ 3,856
Less: reclassification adjustment for net realized gains included in net income, taxes	238	0	1,132
Foreign currency hedge net unrealized loss, tax benefits	(179)	0	0
Less: reclassification adjustment to net income, net of tax benefits of $150, $150 and $150 for 2015, 2014 and 2013, respectively	76	(150)	(150)
Net gains (losses) arising during the period, tax benefits	(27,703)	3,753	(149,364)
Less: amortization of net loss, prior service gain and transition obligation included in net periodic benefit cost, tax benefits	(9,267)	(14,344)	(7,245)
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	$ (18,206)	$ 16,011	$ (132,373)