Changes and Reclassifications Out of Accumulated Other Comprehensive Income (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
Total Reclassifications Out of OCI Current Period [Roll Forward]
Other Comprehensive Income (Loss), Arising During Period, Net of Tax	$ (7,920)	$ 1,884
Accumulated Other Comprehensive Reclass Amounts During Period-Total	6
Accumulated other comprehensive loss	(24,119)	(22,172)	(16,205)
Unrealized securities gains and losses
Total Reclassifications Out of OCI Current Period [Roll Forward]
Accumulated Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	47,504		55,418
Other Comprehensive Income (Loss), Arising During Period, Net of Tax	(7,920)
Accumulated Other Comprehensive Reclass Amounts During Period-Total	6
Pension and postretirement costs
Total Reclassifications Out of OCI Current Period [Roll Forward]
Accumulated Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net of Tax	(71,623)		(71,623)
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net Unamortized Gain (Loss) Arising During Period, Net of Tax	$ 0