Segment Reporting Footnote Tagging (Details)	3 Months Ended
	Mar. 31, 2015 Integer segments properties
Segment Reporting Information [Line Items]
Number of Reportable Segments	5
Number of Available for Sale Securities	57
Number of Variable Interest Entities	11
Mortgage revenue bonds [Member]
Segment Reporting Information [Line Items]
Number of Units in Real Estate Property	7,379
MF Properties [Member]
Segment Reporting Information [Line Items]
Number of Units in Real Estate Property	2,169
Number of Real Estate Properties	6
Consolidated VIEs [Member]
Segment Reporting Information [Line Items]
Number of Units in Real Estate Property	410
Number of Real Estate Properties	2
Number of Variable Interest Entities	2
Public housing capital fund trusts [Member]
Segment Reporting Information [Line Items]
Number of Available for Sale Securities, Public Housing Authorities	3
Unconsolidated Available for Sale Securities [Member]
Segment Reporting Information [Line Items]
Number of Available for Sale Securities	60
Consolidated VIEs [Member]
Segment Reporting Information [Line Items]
Number of Available for Sale Securities	2
Consolidated Properties [Member]
Segment Reporting Information [Line Items]
Number of Real Estate Properties	9
Consolidated Properties [Member] | MF Properties [Member]
Segment Reporting Information [Line Items]
Number of Real Estate Properties	9