Investment Securities Available for Sale - Schedule of Available for Sale Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 674,668	$ 829,738
Unrealized Gains	20,476	16,449
Unrealized Losses	(20,983)	(27,211)
Fair Value	674,161	818,976
Available-for-sale securities
Schedule of Available-for-sale Securities [Line Items]
Investment securities, available for sale, at fair value (including $46,623 and $43,897 held in securitization trusts as of September 30, 2017 and December 31, 2016, respectively, and pledged securities of $493,632 and $690,592, as of September 30, 2017 and December 31, 2016, respectively)	46,623	43,897
Agency ARMs
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	99,338	114,180
Unrealized Gains	34	95
Unrealized Losses	(1,105)	(1,430)
Fair Value	98,267	112,845
Agency ARMs \| Freddie Mac
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	34,733	39,138
Unrealized Gains	21	24
Unrealized Losses	(351)	(528)
Fair Value	34,403	38,634
Agency ARMs \| Fannie Mae
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	59,583	69,031
Unrealized Gains	13	71
Unrealized Losses	(545)	(698)
Fair Value	59,051	68,404
Agency ARMs \| Ginnie Mae
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	5,022	6,011
Unrealized Gains	0	0
Unrealized Losses	(209)	(204)
Fair Value	4,813	5,807
Agency Fixed Rate
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	289,104	339,310
Unrealized Gains	0	0
Unrealized Losses	(9,680)	(10,683)
Fair Value	279,424	328,627
Agency Fixed Rate \| Freddie Mac
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	21,556	26,338
Unrealized Gains	0	0
Unrealized Losses	(586)	(644)
Fair Value	20,970	25,694
Agency Fixed Rate \| Fannie Mae
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	267,169	312,515
Unrealized Gains	0	0
Unrealized Losses	(9,089)	(10,035)
Fair Value	258,080	302,480
Agency Fixed Rate \| Ginnie Mae
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	379	457
Unrealized Gains	0	0
Unrealized Losses	(5)	(4)
Fair Value	374	453
Agency IOs
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	47,033	97,153
Unrealized Gains	486	2,260
Unrealized Losses	(10,178)	(14,522)
Fair Value	37,341	84,891
Agency IOs \| Freddie Mac
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	9,423	19,768
Unrealized Gains	25	559
Unrealized Losses	(2,571)	(3,363)
Fair Value	6,877	16,964
Agency IOs \| Fannie Mae
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	13,752	27,597
Unrealized Gains	50	478
Unrealized Losses	(3,316)	(4,777)
Fair Value	10,486	23,298
Agency IOs \| Ginnie Mae
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	23,858	49,788
Unrealized Gains	411	1,223
Unrealized Losses	(4,291)	(6,382)
Fair Value	19,978	44,629
Agency RMBS
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	435,475	550,643
Unrealized Gains	520	2,355
Unrealized Losses	(20,963)	(26,635)
Fair Value	415,032	526,363
Non-Agency RMBS
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	131,253	162,220
Unrealized Gains	1,789	1,218
Unrealized Losses	(20)	(154)
Fair Value	133,022	163,284
U.S. Treasury Securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	2,920	2,920
Unrealized Gains	4	0
Unrealized Losses	0	(33)
Fair Value	2,924	2,887
CMBS
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	105,020	113,955
Unrealized Gains	18,163	12,876
Unrealized Losses	0	(389)
Fair Value	123,183	126,442
CMBS \| Available-for-sale securities
Schedule of Available-for-sale Securities [Line Items]
Investment securities, available for sale, at fair value (including $46,623 and $43,897 held in securitization trusts as of September 30, 2017 and December 31, 2016, respectively, and pledged securities of $493,632 and $690,592, as of September 30, 2017 and December 31, 2016, respectively)	$ 46,600	$ 43,900

The total amount of cash and securities held by third party trustees pursuant to terms of debt instruments or other agreements as of the date of each statement of financial position presented, which can be used by the trustee only to pay the noncurrent portion of specified obligations.

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-Name Accounting Standards Codification
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Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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-Publisher FASB
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Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

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