Repurchase Agreements (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Average Balance
Repurchase agreement disclosures
Repurchase agreements	$ 12.5	$ 13.7
Maximum
Repurchase agreement disclosures
Repurchase agreements	$ 95.0	$ 65.9