Statements of Consolidated Comprehensive Income (Loss) Statements of Consolidated Comprehensive Income (Loss) (Parenthetical) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Statement of Income and Comprehensive Income (Parenthetical) [Abstract]
Unrealized gain (loss) on available-for-sale security, net of deferred tax of $0, $0 and $145, respectively	$ 0	$ 0	$ 145
Actuarial gain (loss), net of deferred tax of $59,850, $103,308 and $1,903, respectively	59,850	103,308	1,903
Net actuarial loss included in periodic benefit expense or income, net of deferred tax of $9,432, $7,562 and $7,969, respectively	9,432	7,562	7,969
Prior-service cost or credit, net of deferred tax of $0, $7,505 and $17,577, respectively	0	7,505	17,577
Amortization of prior service cost or credit included in net periodic benefit expense or income, net of deferred tax of $481, $552 and $465, respectively	$ 481	$ 552	$ 465