Debt Financing Total Debt Financing (Details) (USD $)					12 Months Ended						12 Months Ended		12 Months Ended			12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2013 Categories of Investments, Marketable Securities, Trading Securities [Member]	Dec. 31, 2012 Categories of Investments, Marketable Securities, Trading Securities [Member]	Dec. 31, 2013 Categories of Investments, Marketable Securities, Trading Securities [Member] TOB facility-2 [Member]	Dec. 31, 2012 Categories of Investments, Marketable Securities, Trading Securities [Member] TOB facility-2 [Member]	Dec. 31, 2013 Categories of Investments, Marketable Securities, Trading Securities [Member] TOB Facility-1 [Member]	Dec. 31, 2012 Categories of Investments, Marketable Securities, Trading Securities [Member] TOB Facility-1 [Member]	Dec. 31, 2013 Categories of Investments, Marketable Securities, Trading Securities [Member] TOB facility-5 [Member]	Mar. 31, 2013 Categories of Investments, Marketable Securities, Trading Securities [Member] TOB facility-5 [Member]	Dec. 31, 2013 Categories of Investments, Marketable Securities, Trading Securities [Member] TOB facility-6 [Member]	Mar. 31, 2013 Categories of Investments, Marketable Securities, Trading Securities [Member] TOB facility-6 [Member]	Dec. 31, 2013 Categories of Investments, Marketable Securities, Trading Securities [Member] TOB facility-7 [Member]		Jun. 30, 2013 Categories of Investments, Marketable Securities, Trading Securities [Member] TOB facility-7 [Member]	Dec. 31, 2013 Categories of Investments, Marketable Securities, Trading Securities [Member] TOB facility-8 [Member]		Dec. 31, 2013 Categories of Investments, Marketable Securities, Trading Securities [Member] TOB facility-9 [Member]	Dec. 31, 2013 Categories of Investments, Marketable Securities, Trading Securities [Member] Mortgage Backed Security Trust 1 [Member] TOB facility-3 [Member]	Dec. 31, 2012 Categories of Investments, Marketable Securities, Trading Securities [Member] Mortgage Backed Security Trust 1 [Member] TOB facility-3 [Member]	Dec. 31, 2013 Categories of Investments, Marketable Securities, Trading Securities [Member] Mortgage Backed Security Trust 2 [Member] TOB facility-3 [Member]	Dec. 31, 2012 Categories of Investments, Marketable Securities, Trading Securities [Member] Mortgage Backed Security Trust 2 [Member] TOB facility-3 [Member]	Dec. 31, 2013 Categories of Investments, Marketable Securities, Trading Securities [Member] Mortgage Backed Security Trust 3 [Member] TOB facility-3 [Member]	Dec. 31, 2012 Categories of Investments, Marketable Securities, Trading Securities [Member] Mortgage Backed Security Trust 3 [Member] TOB facility-3 [Member]	Dec. 31, 2013 Categories of Investments, Marketable Securities, Trading Securities [Member] Mortgage Backed Security Trust 4 [Member] TOB facility-3 [Member]	Dec. 31, 2012 Categories of Investments, Marketable Securities, Trading Securities [Member] Mortgage Backed Security Trust 4 [Member] TOB facility-3 [Member]	Dec. 31, 2013 Categories of Investments, Marketable Securities, Trading Securities [Member] Mortgage Backed Security Trust 5 [Member] [Member] TOB facility-3 [Member]	Dec. 31, 2012 Categories of Investments, Marketable Securities, Trading Securities [Member] Mortgage Backed Security Trust 5 [Member] [Member] TOB facility-3 [Member]	Dec. 31, 2013 Categories of Investments, Marketable Securities, Trading Securities [Member] Mortgage Backed Security Trust 6 [Member] TOB facility-3 [Member]	Jun. 30, 2013 Categories of Investments, Marketable Securities, Trading Securities [Member] Mortgage Backed Security Trust 6 [Member] TOB facility-3 [Member]
Debt Instrument [Line Items]
Debt financing	$ 257,274,000	$ 177,948,000	$ 164,295,000	$ 83,960,000	$ 48,995,000	$ 48,995,000	$ 9,770,000	$ 9,850,000	$ 5,700,000		$ 7,000,000		$ 20,000,000	[1]		$ 13,210,000	[2]	$ 25,750,000	$ 2,585,000	$ 2,585,000	$ 4,090,000	$ 4,090,000	$ 2,865,000	$ 3,890,000	$ 5,960,000	$ 5,960,000	$ 10,545,000	$ 8,590,000	$ 7,825,000
Date of Debt Borrowing					2012	2012	2011	2011	2013		2013		2013	[1]		2013	[2]	2013	2012	2012	2012	2012	2012	2012	2012	2012	2012	2012	2013
Available-for-sale Security, Maturity Date at a point in time					Jun. 01, 2014	Jul. 01, 2013	Jul. 01, 2014	Jul. 01, 2013	Jun. 01, 2014		Aug. 01, 2014		Jun. 01, 2014	[1]		Oct. 01, 2014	[2]	Dec. 01, 2014	Apr. 01, 2014	Oct. 01, 2013	Apr. 01, 2014	Oct. 01, 2013	Apr. 01, 2014	Oct. 01, 2013	Apr. 01, 2014	Oct. 01, 2013	Apr. 01, 2014	Oct. 01, 2013	Aug. 01, 2014
Debt Instrument, Total Rate of Borrowing					2.32%	2.30%	1.96%	2.05%	2.40%	2.60%	2.40%	2.60%	2.21%	[1]	2.50%	2.21%	[2]	1.96%	1.21%	1.31%	1.29%	1.29%	1.22%	1.32%	1.23%	1.29%	1.27%	1.28%	1.02%	1.00%

[1] Avistar at the Oaks Apartments, Avistar on the Hills Apartments, and Avistar in 09 Apartments is the collateral for the $20.0 million TOB Trust.

[2] Avistar at Chase Hill, Avistar at the Crest, and Avistar on the Boulevard is the collateral for the approximate $13.2 million TOB Trust.