Fair Value Measurements Available for sale securities (Details) (USD $) | Mar. 31, 2014 | Dec. 31, 2013 | Mar. 31, 2014 | Dec. 31, 2013 | Mar. 31, 2014 | Dec. 31, 2013 | Mar. 31, 2014 | Dec. 31, 2013 | Mar. 31, 2014 | Dec. 31, 2013 | Mar. 31, 2014 | Dec. 31, 2013 | Mar. 31, 2014 | Dec. 31, 2013 | Mar. 31, 2014 | Dec. 31, 2013 | Mar. 31, 2014 | Dec. 31, 2013 | Mar. 31, 2014 | Dec. 31, 2013 | Mar. 31, 2014 | Dec. 31, 2013 | Mar. 31, 2014 | Dec. 31, 2013 | Mar. 31, 2014 | Dec. 31, 2013 | Mar. 31, 2014 | Dec. 31, 2013 | Mar. 31, 2014 | Dec. 31, 2013 | Mar. 31, 2014 | Dec. 31, 2013 | Mar. 31, 2014 | Dec. 31, 2013 | Mar. 31, 2014 | Dec. 31, 2013 | Mar. 31, 2014 | Mar. 31, 2013 | Dec. 31, 2013 | Mar. 31, 2014 | Mar. 31, 2013 | Dec. 31, 2013 | Mar. 31, 2014 | Mar. 31, 2013 | Dec. 31, 2013 | Mar. 31, 2014 | Dec. 31, 2013 | Mar. 31, 2014 | Mar. 31, 2013 | Dec. 31, 2013 | Mar. 31, 2014 | Mar. 31, 2013 | Dec. 31, 2013 | Mar. 31, 2013 | Mar. 31, 2013 | Mar. 31, 2013 | Mar. 31, 2013 | Mar. 31, 2013 | Dec. 31, 2013 | Dec. 31, 2010 | Mar. 31, 2014 | Mar. 31, 2014 | Mar. 31, 2014 | Mar. 31, 2014 | Mar. 31, 2014 |
Mortgage revenue bonds [Member] | Mortgage revenue bonds [Member] | Public housing capital fund trusts [Member] | Public housing capital fund trusts [Member] | Trust Portfolio--MBS Bonds [Member] | Trust Portfolio--MBS Bonds [Member] | Taxable Bonds [Member] | Taxable Bonds [Member] | Interest rate derivatives [Member] | Interest rate derivatives [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Inputs, Level 3 [Member] | Ohio Properties [Member] | Ohio Properties [Member] | Ohio Properties [Member] | Ohio Properties [Member] | Ohio Properties [Member] | Lost Creek [Member] | Lost Creek [Member] | Lost Creek [Member] | Lost Creek [Member] | Lost Creek [Member] | Lost Creek [Member] | Lost Creek [Member] |
| | | | | | | | | | | | Mortgage revenue bonds [Member] | Mortgage revenue bonds [Member] | Public housing capital fund trusts [Member] | Public housing capital fund trusts [Member] | Trust Portfolio--MBS Bonds [Member] | Trust Portfolio--MBS Bonds [Member] | Taxable Bonds [Member] | Taxable Bonds [Member] | Interest rate derivatives [Member] | Interest rate derivatives [Member] | | | Mortgage revenue bonds [Member] | Mortgage revenue bonds [Member] | Public housing capital fund trusts [Member] | Public housing capital fund trusts [Member] | Trust Portfolio--MBS Bonds [Member] | Trust Portfolio--MBS Bonds [Member] | Taxable Bonds [Member] | Taxable Bonds [Member] | Interest rate derivatives [Member] | Interest rate derivatives [Member] | | | | Mortgage revenue bonds [Member] | Mortgage revenue bonds [Member] | Mortgage revenue bonds [Member] | Public housing capital fund trusts [Member] | Public housing capital fund trusts [Member] | Public housing capital fund trusts [Member] | Trust Portfolio--MBS Bonds [Member] | Trust Portfolio--MBS Bonds [Member] | Taxable Bonds [Member] | Taxable Bonds [Member] | Taxable Bonds [Member] | Interest rate derivatives [Member] | Interest rate derivatives [Member] | Interest rate derivatives [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Inputs, Level 3 [Member] | | | Fair Value, Inputs, Level 3 [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Inputs, Level 3 [Member] |
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Schedule of Available-for-sale Securities [Line Items] | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | | ' | ' | ' | ' | ' | ' |
Equity Method Investment, Quoted Market Value | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | $0 | $0 | $0 | $0 | $0 | $0 | $0 | $0 | $0 | ' | $0 | $0 | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | | ' | ' | ' | ' | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring/Nonrecurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | | ' | ' | ' | ' | ' | ' |
Assets, Fair Value Disclosure | 423,867,608 | 390,184,284 | 316,471,727 | 285,318,171 | 62,070,540 | 62,056,379 | 39,922,601 | 37,845,661 | 4,298,957 | 4,075,953 | 1,103,783 | 888,120 | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | 352,338,623 | 211,005,403 | ' | 285,318,171 | 145,237,376 | ' | 62,056,379 | 65,389,298 | ' | ' | ' | 4,075,953 | 0 | ' | 888,120 | 378,729 | ' | ' | ' | ' | ' | ' | ' | | ' | ' | ' | ' | ' | ' |
Total gains (lossses) (realized/unrealized) [Abstract] | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | | ' | ' | ' | ' | ' | ' |
Gain (Loss) on Investments | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | -175,837 | -104,658 | ' | 0 | 0 | ' | 0 | 0 | ' | ' | ' | 0 | 0 | ' | -175,837 | -104,658 | ' | ' | ' | ' | ' | ' | ' | | ' | ' | ' | ' | ' | ' |
Other than Temporary Impairment Losses, Investments, Portion in Other Comprehensive Income (Loss), before Tax, Including Portion Attributable to Noncontrolling Interest, Available-for-sale Securities | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | 15,953,883 | 2,867,419 | ' | 14,073,020 | 3,628,875 | ' | 1,657,859 | -761,456 | ' | ' | ' | 223,004 | 0 | ' | 0 | 0 | ' | ' | ' | ' | ' | ' | ' | | ' | ' | ' | ' | ' | ' |
Mortgage revenue bonds held in trust, at fair value | 232,276,390 | 216,371,801 | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | 19,581,166 | 19,581,166 | 0 | 0 | 0 | 17,626,172 | [1] | 18,500,000 | ' | ' | ' | ' | ' |
Deriviative at purchase price | 800,000 | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | 391,500 | ' | ' | 0 | ' | ' | 0 | ' | ' | ' | ' | 0 | ' | ' | 391,500 | ' | ' | ' | ' | ' | ' | ' | ' | | ' | ' | ' | ' | ' | ' |
Mortgage revenue bonds, at fair value | 84,195,337 | 68,946,370 | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | | ' | -17,636,138 | -17,636,138 | 0 | 0 | 0 |
Assets, Fair Value Disclosure | 423,867,608 | 390,184,284 | 316,471,727 | 285,318,171 | 62,070,540 | 62,056,379 | 39,922,601 | 37,845,661 | 4,298,957 | 4,075,953 | 1,103,783 | 888,120 | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | 383,945,007 | 271,746,959 | ' | 316,471,727 | 206,859,175 | ' | 62,070,540 | 64,613,713 | ' | ' | ' | 4,298,957 | 0 | ' | 1,103,783 | 274,071 | ' | ' | ' | ' | ' | ' | ' | | ' | ' | ' | ' | ' | ' |
Fair Value Observable inputs (level 2) | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | 39,922,601 | 37,845,661 | 0 | 0 | 0 | 0 | 39,922,601 | 37,845,661 | 0 | ' | 0 | 0 | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | | ' | ' | ' | ' | ' | ' |
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | 34,778,800 | 38,400,000 | ' | 34,778,800 | 38,400,000 | ' | 0 | 0 | ' | ' | ' | 0 | 0 | ' | 0 | 0 | ' | ' | ' | ' | ' | ' | ' | | ' | ' | ' | ' | ' | ' |
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | -1,705,824 | -2,371 | ' | -62,126 | 11,758 | ' | -1,643,698 | -14,129 | ' | ' | ' | 0 | 0 | ' | 0 | 0 | ' | ' | ' | ' | ' | ' | ' | | ' | ' | ' | ' | ' | ' |
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | $383,945,007 | ' | $352,338,623 | $316,471,727 | ' | $285,318,171 | $62,070,540 | ' | $62,056,379 | $0 | $0 | $4,298,957 | ' | $4,075,953 | $1,103,783 | ' | $888,120 | ' | ' | ' | ' | ' | ' | | ' | ' | ' | ' | ' | ' |
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[1] | December 31, 2013Description of mortgage Revenue BondsB Cost adjusted for pay-downsB Unrealized GainsB Unrealized LossB Estimated Fair ValueArbors at Hickory Ridge (2)B $11,576,209B $225,690B $bB $11,801,899Ashley Square (1)B 5,212,000B bB bB 5,212,000Autumn Pines (2)B 12,147,873B bB (195,355)B 11,952,518Avistar at Chase Hill A Bond (2)B 8,960,000B bB (850,752)B 8,109,248Avistar at the Crest A Bond (2)B 8,759,000B bB (1,298,785)B 7,460,215Avistar at the Oaks (2)B 8,354,000B bB (1,103,115)B 7,250,885Avistar in 09 (2)B 7,192,000B bB (588,254)B 6,603,746Avistar on the Boulevard A Bond (2)B 13,760,000B bB (1,306,512)B 12,453,488Avistar on the Hills (2)B 5,389,000B bB (417,724)B 4,971,276Bella Vista (1)B 6,545,000B bB (473,989)B 6,071,011Bridle Ridge (1)B 7,715,000B bB (452,870)B 7,262,130Brookstone (1)B 7,463,641B 841,751B bB 8,305,392Cross Creek (1)B 6,042,297B 1,480,266B bB 7,522,563Greens Property A Bond (2)B 8,437,501B bB (577,426)B 7,860,075Lake Forest (1)B 8,997,000B bB (289,461)B 8,707,539Lost Creek (1)B 15,883,084B 1,743,088B bB 17,626,172Ohio Properties A Bonds (1)B 14,498,000B bB bB 14,498,000Runnymede (1)B 10,525,000B bB (551,510)B 9,973,490Southpark (1)B 11,878,885B 1,018,750B bB 12,897,635The Suites on Paseo (2)B 35,750,000B bB (2,502)B 35,747,498Woodlynn Village (1)B 4,426,000B bB (340,979)B 4,085,021Mortgage revenue bonds held in trustB $219,511,490B $5,309,545B $(8,449,234)B $216,371,801 December 31, 2013Description of Mortgage Revenue BondsB Cost adjusted for pay-downsB Unrealized GainB Unrealized LossB Estimated Fair ValueAvistar at Chase Hill B BondB $2,005,000B $bB $(159,117)B $1,845,883Avistar at the Crest B BondB 1,700,000B bB (134,912)B 1,565,088Avistar on the Boulevard B BondB 3,216,000B bB (255,222)B 2,960,778Copper Gate ApartmentsB 5,220,000B bB (252,648)B 4,967,352Greens Property B BondB 948,291B 189,589B bB 1,137,880Ohio Properties B BondsB 3,583,590B 150,864B bB 3,734,454RenaissanceB 7,975,000B bB (16,964)B 7,958,036The Palms at Premier Park ApartmentsB 20,152,000B bB (283,942)B 19,868,058Tyler Park ApartmentsB 8,100,000B bB (526,601)B 7,573,399Vantage at HarlingenB 6,692,000B bB (211,735)B 6,480,265Vantage at JudsonB 6,049,000B bB (190,423)B 5,858,577Westside VillageB 5,400,000B bB (403,400)B 4,996,600Mortgage revenue bondsB $71,040,881B $340,453B $(2,434,964)B $68,946,370 |