Real Estate Securities Schedule of Real Estate Securities by Weighted Average Life (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Real Estate-Related Securities [Line Items]
Real estate securities, at fair value	$ 1,472,791	$ 13,596
Non-Agency RMBS [Member]
Real Estate-Related Securities [Line Items]
Real estate securities, at fair value	34,467	13,596
Investment Owned, at Cost	33,823	13,490
Weighted Average Coupon Rate, Percent	2.88%	2.20%
Less than three years [Member] \| Non-Agency RMBS [Member]
Real Estate-Related Securities [Line Items]
Real estate securities, at fair value	4,616	3,036
Investment Owned, at Cost	4,291	3,001
Weighted Average Coupon Rate, Percent	1.97%	5.57%
Greater than three years and less than seven years [Member] \| Non-Agency RMBS [Member]
Real Estate-Related Securities [Line Items]
Real estate securities, at fair value	18,188	3,994
Investment Owned, at Cost	18,244	3,978
Weighted Average Coupon Rate, Percent	3.41%	0.61%
Greater than seven years and less than eleven years [Member] \| Non-Agency RMBS [Member]
Real Estate-Related Securities [Line Items]
Real estate securities, at fair value	10,963	3,601
Investment Owned, at Cost	10,477	3,608
Weighted Average Coupon Rate, Percent	1.88%	1.10%
Greater than eleven years [Member] \| Non-Agency RMBS [Member]
Real Estate-Related Securities [Line Items]
Real estate securities, at fair value	700	2,965
Investment Owned, at Cost	811	2,903
Weighted Average Coupon Rate, Percent	7.69%	2.49%
Fixed Rate [Member] \| Agency RMBS [Member]
Real Estate-Related Securities [Line Items]
Real estate securities, at fair value	1,425,602
Investment Owned, at Cost	1,442,897
Weighted Average Coupon Rate, Percent	3.59%
Fixed Rate [Member] \| Less than three years [Member] \| Agency RMBS [Member]
Real Estate-Related Securities [Line Items]
Real estate securities, at fair value	3,859
Investment Owned, at Cost	3,859
Weighted Average Coupon Rate, Percent	6.01%
Fixed Rate [Member] \| Greater than three years and less than seven years [Member] \| Agency RMBS [Member]
Real Estate-Related Securities [Line Items]
Real estate securities, at fair value	243,429
Investment Owned, at Cost	244,043
Weighted Average Coupon Rate, Percent	3.32%
Fixed Rate [Member] \| Greater than seven years and less than eleven years [Member] \| Agency RMBS [Member]
Real Estate-Related Securities [Line Items]
Real estate securities, at fair value	1,160,705
Investment Owned, at Cost	1,177,237
Weighted Average Coupon Rate, Percent	3.64%
Fixed Rate [Member] \| Greater than eleven years [Member] \| Agency RMBS [Member]
Real Estate-Related Securities [Line Items]
Real estate securities, at fair value	17,609
Investment Owned, at Cost	17,758
Weighted Average Coupon Rate, Percent	3.89%
Interest-Only [Member] \| Agency RMBS [Member]
Real Estate-Related Securities [Line Items]
Real estate securities, at fair value	12,722
Investment Owned, at Cost	11,355
Weighted Average Coupon Rate, Percent	4.00%
Interest-Only [Member] \| Less than three years [Member] \| Agency RMBS [Member]
Real Estate-Related Securities [Line Items]
Real estate securities, at fair value	2,169
Investment Owned, at Cost	1,601
Weighted Average Coupon Rate, Percent	5.12%
Interest-Only [Member] \| Greater than three years and less than seven years [Member] \| Agency RMBS [Member]
Real Estate-Related Securities [Line Items]
Real estate securities, at fair value	8,209
Investment Owned, at Cost	7,759
Weighted Average Coupon Rate, Percent	3.77%
Interest-Only [Member] \| Greater than seven years and less than eleven years [Member] \| Agency RMBS [Member]
Real Estate-Related Securities [Line Items]
Real estate securities, at fair value	2,344
Investment Owned, at Cost	1,995
Weighted Average Coupon Rate, Percent	3.50%
Interest-Only [Member] \| Greater than eleven years [Member] \| Agency RMBS [Member]
Real Estate-Related Securities [Line Items]
Real estate securities, at fair value	0
Investment Owned, at Cost	$ 0
Weighted Average Coupon Rate, Percent	0.00%