Stockholders' Equity (Reclassifications in Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other income, net	$ 8,181	$ 22,058	$ 10,826	$ 31,154
Provision for income taxes, investments	(66,584)	(98,413)	(135,884)	(176,791)
Total reclassifications for the period	585	1,992	412	1,565
Accumulated Defined Benefit Plans Adjustment, Net Gain (Loss) Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amortization of pension and other post-retirement items, net loss	(369)	(675)	(703)	(1,327)
Benefits Liability, Net of Tax [Member}
Accumulated Other Comprehensive Income (Loss) [Line Items]
Provision for income taxes, defined benefit plan	142	235	270	460
Total reclassifications for the period	(227)	(440)	(433)	$ (867)
Accumulated Net Investment Gain (Loss) Including Portion Attributable to Noncontrolling Interest [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other income, net	1,267	3,795	1,319
Provision for income taxes, investments	(455)	(1,363)	(474)
Income (loss), including portion attributable to noncontrolling interest	$ 812	$ 2,432	$ 845