Accumulated Other Comprehensive Income Components of Other Comprehensive Income (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2013	Mar. 31, 2012
Accumulated Other Comprehensive Income [Roll Forward]
Beginning Balance	$ 5,675	$ 7,955
Current-period other comprehensive income (loss)	(38)	4,154
Other comprehensive income before reclassifications	1,208	4,719
Ending Balance	5,637	12,109
Unrealized Gains on Investment Securities Not Other-Than-Temporarily Impaired [Member]
Accumulated Other Comprehensive Income [Roll Forward]
Beginning Balance	26,361	27,054
Current-period other comprehensive income (loss)	125	4,584
Ending Balance	24,878	30,825
Unrealized Non-Credit Losses on Other-Than-Temporarily Impaired Debt Securities [Member]
Accumulated Other Comprehensive Income [Roll Forward]
Beginning Balance	613	(1,011)
Current-period other comprehensive income (loss)	1,083	135
Ending Balance	1,696	(876)
Unrecognized Pension and Postretirement Plan Items [Member]
Accumulated Other Comprehensive Income [Roll Forward]
Beginning Balance	(18,481)	(15,134)
Current-period other comprehensive income (loss)	328	214
Ending Balance	(18,153)	(14,920)
Unrealized Effective Portions of Losses on Forward-Starting Interest Rate Swaps [Member]
Accumulated Other Comprehensive Income [Roll Forward]
Beginning Balance	(2,818)	(2,954)
Current-period other comprehensive income (loss)	34	34
Ending Balance	(2,784)	(2,920)
Realized Gain (Loss) on Sale of Investments [Member]
Accumulated Other Comprehensive Income [Roll Forward]
Current-period other comprehensive income (loss)	$ (1,608)	$ (813)

Accumulated change in equity from transactions and other events and circumstances from non-owner sources, net of tax effect, at period end. Excludes Net Income (Loss), and accumulated changes in equity from transactions resulting from investments by owners and distributions to owners. Includes foreign currency translation items, certain pension adjustments, unrealized gains and losses on certain investments in debt and equity securities, other than temporary impairment (OTTI) losses related to factors other than credit losses on available-for-sale and held-to-maturity debt securities that an entity does not intend to sell and it is not more likely than not that the entity will be required to sell before recovery of the amortized cost basis, as well as changes in the fair value of derivatives related to the effective portion of a designated cash flow hedge.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 130

-Paragraph 14, 17, 26

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 220

-SubTopic 10

-Section 45

-Paragraph 11

-URI http://asc.fasb.org/extlink&oid=20435746&loc=d3e637-108580

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 220

-SubTopic 10

-Section 45

-Paragraph 14A

-URI http://asc.fasb.org/extlink&oid=20435746&loc=SL7669686-108580

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 220

-SubTopic 10

-Section 45

-Paragraph 14

-URI http://asc.fasb.org/extlink&oid=20435746&loc=d3e681-108580

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Article 3

Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 31

-Article 5

Reference 7: http://www.xbrl.org/2003/role/presentationRef

-Publisher AICPA

-Name Accounting Principles Board Opinion (APB)

-Number 12

-Paragraph 10

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 8: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name FASB Staff Position (FSP)

-Number FAS115-1/124-1

-Paragraph 15D

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details