Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Changes in accumulated other comprehensive income (loss) by component, including amounts reclassified out of accumulated other comprehensive income (loss) and the related line item in the Statements of Operations where net income is presented
Accumulated other comprehensive income (loss), beginning of the period	$ (96,864)	$ (117,701)
Other comprehensive income, net of tax	3,465	100
Other comprehensive income, net of tax	3,465	100
Accumulated other comprehensive income (loss), end of the period	(93,399)	(117,601)
Investment securities:
Changes in accumulated other comprehensive income (loss) by component, including amounts reclassified out of accumulated other comprehensive income (loss) and the related line item in the Statements of Operations where net income is presented
Accumulated other comprehensive income (loss), beginning of the period	2,527	6,807
Other comprehensive income (loss) before reclassifications, net of tax (expense) benefit of $(1,226) and $72, respectively	2,277	(134)
Realized investment losses, net of tax expense of $519 and $84, respectively	964	156
Impairment losses, net of tax expense of $121 and $42, respectively	224	78
Other comprehensive income, net of tax	3,465	100
Accumulated other comprehensive income (loss), end of the period	5,992	6,907
Pension and other postretirement plans:
Changes in accumulated other comprehensive income (loss) by component, including amounts reclassified out of accumulated other comprehensive income (loss) and the related line item in the Statements of Operations where net income is presented
Accumulated other comprehensive income (loss), beginning of the period	(99,391)	(124,508)
Other comprehensive income (loss) before reclassifications, net of tax	0	0
Amortization of prior service costs, net of tax	0	0
Amortization of net actuarial loss, net of tax	0	0
Other comprehensive income (loss), net of tax	0	0
Accumulated other comprehensive income (loss), end of the period	$ (99,391)	$ (124,508)