Consolidated Statements of Comprehensive Income (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement of Comprehensive Income [Abstract]
Net unrealized gains (losses) on securities arising during the period, tax (benefits)	$ (3,468)	$ (2,886)	$ (3,763)
Reclassification adjustment for net realized gains included in net income, tax expenses	0	0	238
Foreign currency hedge net unrealized loss, tax benefits	0	0	179
Unrealized interest rate hedging gain (loss), net of tax (expense) benefit	(151)	0	0
Reclassification adjustment to net income, (taxes) benefits		(289)	76
Net gains (losses) arising during the period, (taxes) benefits	(9,810)	41,129	(27,703)
Amortization of net loss, prior service gain and transition obligation included in net periodic benefit cost, tax benefits	7,317	10,041	9,267
Reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, (taxes) benefits	$ (2,887)	$ 49,523	$ (18,206)