Shareholders' Equity Changes in Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Accumulated other comprehensive loss	$ (17,722)	$ (37,341)	$ 5,675
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	(2,798)	20,402	(39,261)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	(3,953)	(783)	(3,755)
Reclassification adjustment for loss on derivative financial instruments included in net income	2,456	0	0
Accumulated other comprehensive loss	(22,017)	(17,722)	(37,341)
Accumulated Net Unrealized Investment Gain (Loss) [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Accumulated other comprehensive loss	5,980	(27,510)	26,362
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	(7,717)	33,734	(49,607)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	(4,762)	(244)	(4,265)
Accumulated other comprehensive loss	(6,499)	5,980	(27,510)
Accumulated Other-than-Temporary Impairment [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Accumulated other comprehensive loss	1,349	1,652	613
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	239	780	1,977
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	(1,130)	(1,083)	(938)
Accumulated other comprehensive loss	458	1,349	1,652
Accumulated Defined Benefit Plans Adjustment [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Accumulated other comprehensive loss	(22,505)	(8,801)	(18,482)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	4,680	(14,112)	8,369
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	1,864	408	1,312
Accumulated other comprehensive loss	(15,961)	(22,505)	(8,801)
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Accumulated other comprehensive loss	(2,546)	(2,682)	(2,818)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	75	136	136
Reclassification adjustment for loss on derivative financial instruments included in net income	2,456
Accumulated other comprehensive loss	$ (15)	$ (2,546)	$ (2,682)