Summary of Significant Accounting Policies (Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss	$ (11,245)	$ (8,313)	$ (1,343)
Accumulated Net Unrealized Investment Gain (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss	9,869	12,048	18,102
Accumulated other comprehensive (loss) income, tax effect	6,272	7,758	12,706
Accumulated Net Unrealized Long-Term Equity Method Investment Gain (Loss) Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss	0	0	(1,658)
Accumulated other comprehensive (loss) income, tax effect	0	0	1,156
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss	(2)	(19)	(55)
Accumulated other comprehensive (loss) income, tax effect	0	11	36
Accumulated Defined Benefit Plans Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss	(21,112)	(20,342)	(17,732)
Accumulated other comprehensive (loss) income, tax effect	$ 14,491	$ 13,977	$ 12,167