Commitments and Contingencies (Details 2) (USD $) In Millions, unless otherwise specified	12 Months Ended			12 Months Ended
	Dec. 31, 2012 item	Dec. 31, 2012 Belmont	Dec. 31, 2011 Belmont	Dec. 31, 2012 Property and rental value coverage
Commitments and Contingencies
Number of property insurance portfolios for which all-risk property and rental value coverage is maintained	2
Blanket limit per occurrence maintained under first property portfolio				$ 775.0
Limit per occurrence maintained under second property portfolio				750.0
Limit per occurrence and in aggregate per location under liability policies				201.0
Loss reserves		6.2	6.4
Amount of flood coverage				$ 100.0