Investments (Narrative) (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2013 security	Jun. 30, 2012	Dec. 31, 2012
Schedule of Investments [Line Items]
Credit-related net investment impairment losses		$ 0.3
Pooled trust preferred securities, estimated fair value	2.5
Regional community bank stocks, percent of average trading volumes (less than 0.1%)		0.10%
Number Of Pooled Trust Preferred Securities	5
Pooled trust preferred securities, book value	4.9
Annual prepayment rate	1.00%
Annual prepayments maturity	100.00%
Additional basis points	1.50%
Carrying value of securities pledged	231		228
Minimum [Member]
Schedule of Investments [Line Items]
Equity ownership positions in the community bank holding companies	2.00%
Maximum [Member]
Schedule of Investments [Line Items]
Equity ownership positions in the community bank holding companies	5.00%
Pooled Bank Trust Preferred Securities [Member]
Schedule of Investments [Line Items]
Remaining book value		$ 3.3