Significant Accounting Policies (Restricted Asset and Interest Rate Swap Contracts) (Details) (USD $) In Millions, unless otherwise specified			3 Months Ended	12 Months Ended	3 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Jun. 30, 2010 2007 Swap [Member]	Dec. 31, 2010 2007 Swap [Member]	Jun. 30, 2010 2009 Swap [Member]
Significant Accounting Policies [Line Items]
Restricted cash and cash equivalents	$ 0.8	$ 5.3
Pretax loss in connection with termination and settlement agreement			5.4		0.2
Investment securities held by trustees or agencies	$ 25.5	$ 20.7
Interest rate on SWAP				4.294%