Investments in Tax-Exempt Bonds Woodland Park Information (Details) (Woodland Park [Member])	Mar. 31, 2013	Dec. 31, 2012 Unit
Number of Units in Real Estate Property		236
occupancy percentage	88.00%	89.00%
unit occupied [Member]
Number of Units in Real Estate Property	208	211

The number of units in a real estate property owned as of the balance sheet date.

No definition available.

Name:	us-gaap_NumberOfUnitsInRealEstateProperty
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant