Consolidated Statements of Comprehensive Income (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statement of Comprehensive Income [Abstract]
Net unrealized gains (losses) on securities arising during the period, tax (benefits)	$ 10,024	$ (3,468)	$ (2,886)
Reclassification adjustment for net realized gains included in net income, tax expenses	175	0	0
Foreign currency hedge net unrealized loss, taxes (benefits)	(409)	(151)	0
Reclassification adjustment to net income, taxes (benefits)	0	0	(289)
Net gains (losses) arising during the period, taxes (benefits)	3,892	(9,810)	41,129
Amortization of net loss, prior service gain and transition obligation included in net periodic benefit cost, tax benefits	(3,512)	(7,317)	(10,041)
Reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, (taxes) benefits	$ (5,610)	$ 2,887	$ (49,523)