Long-Term Debt Tender Offer (Details) (Tender Offer [Member], USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2010	Dec. 31, 2011 Notes Payable to Banks [Member] Senior Debentures April 2028 [Member]	May 12, 2010 Notes Payable to Banks [Member] Senior Debentures April 2028 [Member]	Apr. 27, 2010 Notes Payable to Banks [Member] Senior Debentures April 2028 [Member]	May 12, 2010 Notes Payable to Banks [Member] Senior Debentures April 2028 Preferred Plus [Member]	Dec. 31, 2011 Notes Payable to Banks [Member] Senior Debentures August 2014 [Member]	May 12, 2010 Notes Payable to Banks [Member] Senior Debentures August 2014 [Member]	Apr. 27, 2010 Notes Payable to Banks [Member] Senior Debentures August 2014 [Member]	Dec. 31, 2011 Subordinated Debt [Member] Deferrable Interest Subordinated Noted Due April 2012 [Member]	May 12, 2010 Subordinated Debt [Member] Deferrable Interest Subordinated Noted Due April 2012 [Member]	Apr. 27, 2010 Subordinated Debt [Member] Deferrable Interest Subordinated Noted Due April 2012 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount		$ 100.0				$ 150.0			$ 100.0
Debt Instrument, Interest Rate, Stated Percentage		7.55%				5.70%			8.50%
Percentage Of Acceptance From Tender Offers			40.35%	50.00%	48.50%		99.20%	99.00%		65.20%	64.00%
Unsolicited Tender Offer Costs	$ 2.7