CYS Investments 10-Q 18 Oct 13 2013 Q3 Quarterly report Financial data

Document_And_Entity_Informatio

Document And Entity Information	9 Months Ended
	Sep. 30, 2013	Oct. 18, 2013
Document Information [Line Items]
Document Type	10-Q
Amendment Flag	FALSE
Document Period End Date	30-Sep-13
Document Fiscal Period Focus	Q3
Document Fiscal Year Focus	2013
Entity Registrant Name	CYS Investments, Inc.
Entity Central Index Key	1396446
Current Fiscal Year End Date	-19
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		166,894,242

Condensed_Statements_Of_Assets

Condensed Statements Of Assets And Liabilities (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, except Per Share data, unless otherwise specified
ASSETS:
Investments in securities, at fair value (including pledged assets of $12,407,463 and $14,831,648, respectively)	$14,456,252	$20,861,718	[1]
Derivative assets, at fair value	267,409	124,169	[1]
Cash and cash equivalents	10,597	13,882	[1]
Receivable for securities sold and principal repayments	744,491	10,343	[1]
Interest receivable	38,773	46,558	[1]
Other assets	892	826	[1]
Total assets	15,518,414	21,057,496	[1]
LIABILITIES:
Repurchase agreements	11,735,071	13,981,307	[1]
Derivative liabilities, at fair value	49,537	98,575	[1]
Payable for securities purchased	1,656,724	4,515,501	[1]
Payable for cash received as collateral	35,488	28,910	[1]
Distribution payable	61,149	1,243	[1]
Accrued interest payable (including accrued interest on repurchase agreements of $2,865 and $11,717, respectively)	15,139	28,863	[1]
Accrued expenses and other liabilities	5,219	435	[1]
Total liabilities	13,558,327	18,654,834	[1]
Commitments and contingencies (note 6)	0	0	[1]
NET ASSETS	1,960,087	2,402,662	[1]
Net assets consist of:
7.75% Series A Cumulative Redeemable Preferred Stock, (3,000 and 3,000 shares issued and outstanding, respectively, $75,000 in aggregate liquidation preference)	72,369	72,369	[1]
7.50% Series B Cumulative Redeemable Preferred Stock, (8,000 and 0 shares issued and outstanding, respectively, $200,000 in aggregate liquidation preference)	193,550	0	[1]
Common Stock, $0.01 par value, 500,000 shares authorized (166,880 and 174,924 shares issued and outstanding, respectively)	1,669	1,749	[1]
Additional paid in capital	2,167,393	2,237,512	[1]
Retained earnings (accumulated deficit)	($474,894)	$91,032	[1]
NET ASSET VALUE PER COMMON SHARE	$10.10	$13.31	[1]
[1]	Derived from audited financial statements.

Condensed_Statements_Of_Assets1

Condensed Statements Of Assets And Liabilities (Parenthetical) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, except Share data, unless otherwise specified
Common Stock, Number of Shares, Par Value and Other Disclosures [Abstract]
Investments in securities, pledged assets	$12,407,463	$14,831,648
Accrued interest payable, accrued interest on repurchase agreements	2,865	11,717
Series Cumulative Redeemable Preferred Stock, par value	$0.01	$0.01
Preferred Stock, shares authorized	50,000,000	50,000,000
Series A Cumulative Redeemable Preferred Stock, shares issued	3,000,000	3,000,000
Series A Cumulative Redeemable Preferred Stock, shares outstanding	3,000,000	3,000,000
Series A Cumulative Redeemable Preferred Stock, aggregate liquidation value	75,000	75,000
Series A Cumulative Redeemable Preferred Stock, liquidation preference per share	$25	$25
Series B Cumulative Redeemable Preferred Stock, shares issued	8,000,000	0
Series B Cumulative Redeemable Preferred Stock, shares outstanding	8,000,000	0
Series B Cumulative Redeemable Preferred Stock, aggregate liquidation value	$200,000	$0
Series B Cumulative Redeemable Preferred Stock, liquidation preference per share	$25	$25
Common stock, par value	$0.01	$0.01
Common stock, shares authorized	500,000,000	500,000,000
Common stock, shares issued	166,880,305	174,924,149
Common stock, shares outstanding	166,880,305	174,924,149

Condensed_Schedules_Of_Investm

Condensed Schedules Of Investments (USD $)	Sep. 30, 2013		Dec. 31, 2012
Investment Holdings [Line Items]
Financial Instruments, Owned, at Fair Value	$14,456,252,000		$20,861,718,000	[1]
Fixed Income Securities [Member]
Investment Holdings [Line Items]
Percent of Investments in Securities	737.50%	[2]	868.30%	[2]
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount	13,987,280,000		19,681,502,000
Financial Instruments, Owned, at Fair Value	14,449,307,000		20,804,143,000
Percent of Investments in Securities	737.20%	[2]	865.90%	[2]
Cost	14,346,058		20,560,760
US Treasury Bill [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount			38,000,000
Financial Instruments, Owned, at Fair Value			37,999,000
Percent of Investments in Securities			1.60%	[2]
Cost			37,995
Other Investments [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount	6,945,000		20,473,000	[2],[3]
Financial Instruments, Owned, at Fair Value	6,945,000		19,576,000	[2],[3]
Percent of Investments in Securities	0.30%	[2]	0.80%	[2],[3]
Cost	6,945	[3]	12,855	[2],[3]
Investments In Securities [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount	13,994,225,000		19,739,975,000
Financial Instruments, Owned, at Fair Value	14,456,252,000		20,861,718,000
Cost	14,353,003		20,611,610
Interest Rate Cap Contracts [Member]
Investment Holdings [Line Items]
Financial Instruments, Owned, at Fair Value	215,992,000		122,989,000
Derivative, Notional Amount	3,900,000,000		3,400,000,000
Percent of Investments in Securities	11.00%	[2],[4]	5.10%	[2],[4]
Cost	143,373		134,815
Interest Rate Swap [Member]
Investment Holdings [Line Items]
Financial Instruments, Owned, at Fair Value	1,880,000		-97,395,000
Derivative, Notional Amount	7,090,000,000		7,490,000,000
Percent of Investments in Securities	-0.10%	[2],[4]	-4.10%	[2],[4]
Cost	0
Derivative, Fixed Interest Rate			0.00%
Federal Home Loan Mortgage Corporation Certificates and Obligations (FHLMC) [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount	2,546,894,000		871,029,000
Financial Instruments, Owned, at Fair Value	2,604,026,000		913,223,000
Percent of Investments in Securities	132.80%	[2]	38.00%	[2]
Fannie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount	11,349,467,000		18,695,972,000
Financial Instruments, Owned, at Fair Value	11,749,900,000		19,768,633,000
Percent of Investments in Securities	599.50%	[2]	822.80%	[2]
Ginnie Mae Pools [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount	90,919,000		114,501,000
Financial Instruments, Owned, at Fair Value	95,381,000		122,287,000
Percent of Investments in Securities	4.90%	[2]	5.10%	[2]
2.15%, due 10/1/2042 - 2/1/2043 (a)(b) | Fannie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount	132,758,000	[5],[6]
Financial Instruments, Owned, at Fair Value	133,571,000	[5],[6]
2.18%, due 11/1/2042 (a)(b) | Fannie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount	29,783,000	[5],[6]	34,926,000	[7]
Financial Instruments, Owned, at Fair Value	30,001,000	[5],[6]	36,246,000	[7]
2.24%, due 10/1/2042 (a)(b) | Fannie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount	47,341,000	[5],[6]	49,605,000	[7]
Financial Instruments, Owned, at Fair Value	47,928,000	[5],[6]	51,511,000	[7]
2.26%, due 11/1/2042 (a)(b) | Fannie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount	40,479,000	[5],[6]	45,372,000	[7]
Financial Instruments, Owned, at Fair Value	40,891,000	[5],[6]	47,149,000	[7]
2.34%, due 11/1/2042 (a)(b) | Fannie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount	65,636,000	[5],[6]
Financial Instruments, Owned, at Fair Value	66,511,000	[5],[6]
2.37%, due 1/1/2043 (a)(b) | Fannie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount	86,645,000	[5],[6]
Financial Instruments, Owned, at Fair Value	87,704,000	[5],[6]
2.39%, due 10/1/2042 (a)(b) | Fannie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount	20,662,000	[5],[6]
Financial Instruments, Owned, at Fair Value	20,932,000	[5],[6]
2.40%, due 9/1/2042 (a)(b) | Fannie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount	32,783,000	[5],[6]
Financial Instruments, Owned, at Fair Value	33,217,000	[5],[6]
2.41%, due 11/1/2042 (a)(b) | Fannie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount	65,178,000	[5],[6]
Financial Instruments, Owned, at Fair Value	66,071,000	[5],[6]
2.42%, due 9/1/2042 - 10/1/2042 (a)(b) | Fannie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount	180,583,000	[5],[6]
Financial Instruments, Owned, at Fair Value	183,074,000	[5],[6]
2.43%, due 6/1/2042 - 1/1/2043 (a)(b) | Fannie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount	111,899,000	[5],[6]
Financial Instruments, Owned, at Fair Value	113,528,000	[5],[6]
2.50%, due 10/1/2042 (a)(b) | Fannie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount	77,970,000	[5],[6]
Financial Instruments, Owned, at Fair Value	79,258,000	[5],[6]
2.51%, due 10/1/2042 (a)(b) | Fannie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount	46,267,000	[5],[6]
Financial Instruments, Owned, at Fair Value	47,004,000	[5],[6]
2.58%, due 8/1/2042 (a)(b) | Fannie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount	30,257,000	[5],[6]	34,217,000	[7],[8]
Financial Instruments, Owned, at Fair Value	30,797,000	[5],[6]	35,801,000	[7],[8]
2.60%, due 4/1/2042 (a)(b) | Fannie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount	32,122,000	[5],[6]
Financial Instruments, Owned, at Fair Value	32,835,000	[5],[6]
2.70%, due 6/1/2042 (a)(b) | Fannie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount	57,465,000	[5],[6]	67,729,000	[7],[8]
Financial Instruments, Owned, at Fair Value	58,724,000	[5],[6]	70,933,000	[7],[8]
2.79%, due 4/1/2042 (a)(b) | Fannie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount	139,002,000	[5],[6]
Financial Instruments, Owned, at Fair Value	143,813,000	[5],[6]
2.80%, due 2/1/2042 - 4/1/2042 (a)(b) | Fannie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount	88,947,000	[5],[6]
Financial Instruments, Owned, at Fair Value	91,824,000	[5],[6]
2.83%, due 2/1/2042 (a)(b) | Fannie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount	27,652,000	[5],[6]
Financial Instruments, Owned, at Fair Value	28,494,000	[5],[6]
2.84%, due 12/1/2041 (a)(b) | Fannie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount	45,003,000	[5],[6]
Financial Instruments, Owned, at Fair Value	46,680,000	[5],[6]
3.00%, due 2/1/2027 - 10/1/2028 (a) | Fannie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount	4,620,867,000	[5]
Financial Instruments, Owned, at Fair Value	4,787,923,000	[5]
3.00%, due 12/1/2037 (a) | Fannie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount	51,729,000	[5]
Financial Instruments, Owned, at Fair Value	50,900,000	[5]
3.00%, due 10/1/2042 (a) | Fannie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount	42,959,000	[5]	46,277,000	[8]
Financial Instruments, Owned, at Fair Value	41,465,000	[5]	47,556,000	[8]
3.06%, due 9/1/2041 (a)(b) | Fannie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount	28,807,000	[5],[6]
Financial Instruments, Owned, at Fair Value	29,870,000	[5],[6]
3.24%, due 3/1/2041(a)(b) | Fannie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount	12,056,000	[6]	15,547,000	[7],[8]
Financial Instruments, Owned, at Fair Value	12,580,000	[6]	16,389,000	[7],[8]
3.35%, due 5/1/2041 (a)(b) | Fannie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount	14,785,000	[5],[6]
Financial Instruments, Owned, at Fair Value	15,424,000	[5],[6]
3.36%, due 8/1/2041 (a)(b) | Fannie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount	22,336,000	[5],[6]
Financial Instruments, Owned, at Fair Value	23,267,000	[5],[6]
3.50%, due 12/1/2025 - 10/1/2028 (a) | Fannie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount	953,512,000	[5]
Financial Instruments, Owned, at Fair Value	1,006,774,000	[5]
3.50%, due 6/1/2042 - 10/1/2043 (a) | Fannie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount	2,148,929,000	[5]
Financial Instruments, Owned, at Fair Value	2,190,239,000	[5]
3.98%, due 9/1/2039 (b) | Fannie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount	8,139,000	[6]
Financial Instruments, Owned, at Fair Value	8,575,000	[6]
4.00%, due 1/1/2026 - 4/1/2026 (a) | Fannie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount	244,812,000	[5]
Financial Instruments, Owned, at Fair Value	259,903,000	[5]
4.00%, due 7/1/2043 - 10/1/2043 (a) | Fannie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount	1,544,256,000	[5]
Financial Instruments, Owned, at Fair Value	1,620,828,000	[5]
4.50%, due 4/1/2030 - 11/1/2030 (a) | Fannie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount	89,615,000	[5]
Financial Instruments, Owned, at Fair Value	96,643,000	[5]
4.50%, due 11/1/2041 (a) | Fannie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount	208,233,000	[5]
Financial Instruments, Owned, at Fair Value	222,652,000	[5]
2.19%, due 2/1/2043 (a)(b) | Federal Home Loan Mortgage Corporation Certificates and Obligations (FHLMC) [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount	28,951,000	[5],[6]
Financial Instruments, Owned, at Fair Value	29,052,000	[5],[6]
2.22%, due 12/1/2042 (a)(b) | Federal Home Loan Mortgage Corporation Certificates and Obligations (FHLMC) [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount	44,420,000	[5],[6]	50,184,000	[7]
Financial Instruments, Owned, at Fair Value	44,759,000	[5],[6]	52,100,000	[7]
2.29%, due 11/1/2042 (a)(b) | Federal Home Loan Mortgage Corporation Certificates and Obligations (FHLMC) [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount	93,202,000	[5],[6]
Financial Instruments, Owned, at Fair Value	94,062,000	[5],[6]
2.43%, due 6/1/2042 (a)(b) | Federal Home Loan Mortgage Corporation Certificates and Obligations (FHLMC) [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount	35,541,000	[5],[6]	38,618,000	[7],[8]
Financial Instruments, Owned, at Fair Value	36,146,000	[5],[6]	40,336,000	[7],[8]
2.44%, due 4/1/2043 (a)(b) | Federal Home Loan Mortgage Corporation Certificates and Obligations (FHLMC) [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount	30,125,000	[5],[6]
Financial Instruments, Owned, at Fair Value	29,591,000	[5],[6]
2.45%, due 7/1/2042 (a)(b) | Federal Home Loan Mortgage Corporation Certificates and Obligations (FHLMC) [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount	39,773,000	[5],[6]	46,980,000	[7],[8]
Financial Instruments, Owned, at Fair Value	40,393,000	[5],[6]	49,027,000	[7],[8]
2.52%, due 11/1/2042 (a)(b) | Federal Home Loan Mortgage Corporation Certificates and Obligations (FHLMC) [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount	37,992,000	[5],[6]
Financial Instruments, Owned, at Fair Value	38,627,000	[5],[6]
2.54%, due 7/1/2042 (a)(b) | Federal Home Loan Mortgage Corporation Certificates and Obligations (FHLMC) [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount	35,605,000	[5],[6]	41,200,000	[7],[8]
Financial Instruments, Owned, at Fair Value	36,296,000	[5],[6]	43,077,000	[7],[8]
2.56%, due 2/1/2043 (a)(b) | Federal Home Loan Mortgage Corporation Certificates and Obligations (FHLMC) [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount	113,721,000	[5],[6]
Financial Instruments, Owned, at Fair Value	112,544,000	[5],[6]
2.59%, due 3/1/2042 (a)(b) | Federal Home Loan Mortgage Corporation Certificates and Obligations (FHLMC) [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount	30,501,000	[5],[6]	35,421,000	[7],[8]
Financial Instruments, Owned, at Fair Value	31,322,000	[5],[6]	37,203,000	[7],[8]
2.79%, due 12/1/2041 (a)(b) | Federal Home Loan Mortgage Corporation Certificates and Obligations (FHLMC) [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount	35,177,000	[5],[6]	42,260,000	[7],[8]
Financial Instruments, Owned, at Fair Value	36,197,000	[5],[6]	44,357,000	[7],[8]
3.31%, due 1/1/2041 (a)(b) | Federal Home Loan Mortgage Corporation Certificates and Obligations (FHLMC) [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount	28,117,000	[5],[6]
Financial Instruments, Owned, at Fair Value	29,474,000	[5],[6]
3.50%, due 4/1/2026 - 2/1/2027 (a) | Federal Home Loan Mortgage Corporation Certificates and Obligations (FHLMC) [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount	138,332,000	[5]
Financial Instruments, Owned, at Fair Value	145,704,000	[5]
3.50%, due 5/1/2043 - 7/1/2043 (a) | Federal Home Loan Mortgage Corporation Certificates and Obligations (FHLMC) [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount	1,368,831,000	[5]
Financial Instruments, Owned, at Fair Value	1,390,517,000	[5]
4.00%, due 8/1/2043 - 10/1/2043 (a) | Federal Home Loan Mortgage Corporation Certificates and Obligations (FHLMC) [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount	448,594,000	[5]
Financial Instruments, Owned, at Fair Value	469,139,000	[5]
4.50%, due 12/1/2024 - 5/1/2025 (a) | Federal Home Loan Mortgage Corporation Certificates and Obligations (FHLMC) [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount	38,012,000	[5]
Financial Instruments, Owned, at Fair Value	40,203,000	[5]
3.50%, due 7/20/2040 (a)(b) | Ginnie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount	81,800,000	[5],[6]	101,626,000	[7],[8]
Financial Instruments, Owned, at Fair Value	85,760,000	[5],[6]	108,469,000	[7],[8]
4.00%, due 1/20/2040 (a)(b) | Ginnie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount	9,119,000	[5],[6]
Financial Instruments, Owned, at Fair Value	9,621,000	[5],[6]
10/15/2015 | Interest Rate Cap Contracts [Member]
Investment Holdings [Line Items]
Financial Instruments, Owned, at Fair Value	306,000		386,000
Derivative, Notional Amount	300,000,000		300,000,000
Derivative, Cap Interest Rate	1.43%
11/8/2015 | Interest Rate Cap Contracts [Member]
Investment Holdings [Line Items]
Financial Instruments, Owned, at Fair Value	255,000		302,000
Derivative, Notional Amount	200,000,000		200,000,000
Derivative, Cap Interest Rate	1.36%
5/23/2019 | Interest Rate Cap Contracts [Member]
Investment Holdings [Line Items]
Financial Instruments, Owned, at Fair Value	11,645,000		6,714,000
Derivative, Notional Amount	300,000,000		300,000,000
Derivative, Cap Interest Rate	2.00%
6/1/2019 | Interest Rate Cap Contracts [Member]
Investment Holdings [Line Items]
Financial Instruments, Owned, at Fair Value	13,307,000		7,553,000
Derivative, Notional Amount	300,000,000		300,000,000
Derivative, Cap Interest Rate	1.75%
6/29/2019 | Interest Rate Cap Contracts [Member]
Investment Holdings [Line Items]
Financial Instruments, Owned, at Fair Value	15,481,000		8,686,000
Derivative, Notional Amount	300,000,000		300,000,000
Derivative, Cap Interest Rate	1.50%
7/2/2019 | Interest Rate Cap Contracts [Member]
Investment Holdings [Line Items]
Financial Instruments, Owned, at Fair Value	15,852,000		9,165,000
Derivative, Notional Amount	300,000,000		300,000,000
Derivative, Cap Interest Rate	1.50%
7/16/2019 | Interest Rate Cap Contracts [Member]
Investment Holdings [Line Items]
Financial Instruments, Owned, at Fair Value	28,839,000		17,255,000
Derivative, Notional Amount	500,000,000		500,000,000
Derivative, Cap Interest Rate	1.25%
3/26/2020 | Interest Rate Cap Contracts [Member]
Investment Holdings [Line Items]
Financial Instruments, Owned, at Fair Value	38,213,000
Derivative, Notional Amount	500,000,000
Derivative, Cap Interest Rate	1.25%
3/30/2020 | Interest Rate Cap Contracts [Member]
Investment Holdings [Line Items]
Financial Instruments, Owned, at Fair Value	52,826,000
Derivative, Notional Amount	700,000,000
Derivative, Cap Interest Rate	1.25%
5/20/2020 | Interest Rate Cap Contracts [Member]
Investment Holdings [Line Items]
Financial Instruments, Owned, at Fair Value	39,268,000
Derivative, Notional Amount	500,000,000
Derivative, Cap Interest Rate	1.25%
7/1/2014 | Interest Rate Swap [Member]
Investment Holdings [Line Items]
Financial Instruments, Owned, at Fair Value	-1,071,000		-2,049,000
Derivative, Notional Amount	100,000,000		100,000,000
Derivative, Fixed Interest Rate	1.72%		1.72%
7/16/2014 | Interest Rate Swap [Member]
Investment Holdings [Line Items]
Financial Instruments, Owned, at Fair Value	-2,838,000		-5,309,000
Derivative, Notional Amount	250,000,000		250,000,000
Derivative, Fixed Interest Rate	1.73%		1.73%
8/16/2014 | Interest Rate Swap [Member]
Investment Holdings [Line Items]
Financial Instruments, Owned, at Fair Value	-1,840,000		-3,246,000
Derivative, Notional Amount	200,000,000		200,000,000
Derivative, Fixed Interest Rate	1.35%		1.35%
9/23/2014 | Interest Rate Swap [Member]
Investment Holdings [Line Items]
Financial Instruments, Owned, at Fair Value	-4,890,000		-8,167,000
Derivative, Notional Amount	500,000,000		500,000,000
Derivative, Fixed Interest Rate	1.31%		1.31%
10/6/2014 | Interest Rate Swap [Member]
Investment Holdings [Line Items]
Financial Instruments, Owned, at Fair Value	-2,081,000		-3,405,000
Derivative, Notional Amount	240,000,000		240,000,000
Derivative, Fixed Interest Rate	1.17%		1.17%
2/14/2015 | Interest Rate Swap [Member]
Investment Holdings [Line Items]
Financial Instruments, Owned, at Fair Value	-12,309,000		-18,564,000
Derivative, Notional Amount	500,000,000		500,000,000
Derivative, Fixed Interest Rate	2.15%		2.15%
6/2/2016 | Interest Rate Swap [Member]
Investment Holdings [Line Items]
Financial Instruments, Owned, at Fair Value	-10,320,000		-14,320,000
Derivative, Notional Amount	300,000,000		300,000,000
Derivative, Fixed Interest Rate	1.94%		1.94%
12/19/2016 | Interest Rate Swap [Member]
Investment Holdings [Line Items]
Financial Instruments, Owned, at Fair Value	-4,649,000		-7,996,000
Derivative, Notional Amount	250,000,000		250,000,000
Derivative, Fixed Interest Rate	1.43%		1.43%
4/24/2017 | Interest Rate Swap [Member]
Investment Holdings [Line Items]
Financial Instruments, Owned, at Fair Value	-5,888,000		-11,556,000	[9]
Derivative, Notional Amount	500,000,000		500,000,000	[9]
Derivative, Fixed Interest Rate	1.31%		1.31%	[9]
7/13/2017 | Interest Rate Swap [Member]
Investment Holdings [Line Items]
Financial Instruments, Owned, at Fair Value	5,711,000		-4,117,000
Derivative, Notional Amount	750,000,000		750,000,000
Derivative, Fixed Interest Rate	0.86%		0.86%
9/6/2017 | Interest Rate Swap [Member]
Investment Holdings [Line Items]
Financial Instruments, Owned, at Fair Value	3,500,000		33,000
Derivative, Notional Amount	250,000,000		250,000,000
Derivative, Fixed Interest Rate	0.77%		0.77%
9/6/2017 | Interest Rate Swap [Member]
Investment Holdings [Line Items]
Financial Instruments, Owned, at Fair Value	6,845,000
Derivative, Notional Amount	500,000,000
Derivative, Fixed Interest Rate	0.77%
9/6/2017 | Interest Rate Swap [Member]
Investment Holdings [Line Items]
Financial Instruments, Owned, at Fair Value	3,570,000
Derivative, Notional Amount	250,000,000
Derivative, Fixed Interest Rate	0.77%
11/29/2017(f) | Interest Rate Swap [Member]
Investment Holdings [Line Items]
Financial Instruments, Owned, at Fair Value	7,671,000	[10]	1,121,000	[10]
Derivative, Notional Amount	500,000,000	[10]	500,000,000	[10]
Derivative, Fixed Interest Rate	0.87%	[10]	0.87%	[10]
2/21/2018 | Interest Rate Swap [Member]
Investment Holdings [Line Items]
Financial Instruments, Owned, at Fair Value	6,265,000
Derivative, Notional Amount	500,000,000
Derivative, Fixed Interest Rate	1.02%
2/27/2018 | Interest Rate Swap [Member]
Investment Holdings [Line Items]
Financial Instruments, Owned, at Fair Value	7,770,000
Derivative, Notional Amount	500,000,000
Derivative, Fixed Interest Rate	0.96%
4/25/2018(g) | Interest Rate Swap [Member]
Investment Holdings [Line Items]
Financial Instruments, Owned, at Fair Value	10,085,000	[11]
Derivative, Notional Amount	500,000,000	[11]
Derivative, Fixed Interest Rate	1.01%	[11]
8/15/2018 | Interest Rate Swap [Member]
Investment Holdings [Line Items]
Financial Instruments, Owned, at Fair Value	-3,651,000
Derivative, Notional Amount	500,000,000
Derivative, Fixed Interest Rate	1.65%
2.15%, due 2/1/2043(b) | Fannie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount			100,000,000	[7]
Financial Instruments, Owned, at Fair Value			103,991,000	[7]
2.16%, due 10/1/2042(b) | Fannie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount			44,800,000	[7]
Financial Instruments, Owned, at Fair Value			46,452,000	[7]
2.17%, due 3/1/2043(b) | Fannie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount			30,000,000	[7]
Financial Instruments, Owned, at Fair Value			31,167,000	[7]
2.34%, due 11/1/2042(b) | Fannie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount			75,085,000	[7]
Financial Instruments, Owned, at Fair Value			78,162,000	[7]
2.38%, due 1/1/2043(a)(b) | Fannie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount			100,237,000	[7],[8]
Financial Instruments, Owned, at Fair Value			104,444,000	[7],[8]
2.40%, due 9/1/2042 - 10/1/2042(a)(b) | Fannie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount			63,216,000	[7],[8]
Financial Instruments, Owned, at Fair Value			65,915,000	[7],[8]
2.41%, due 7/1/2042 - 9/1/2042(a)(b) | Fannie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount			69,629,000	[7],[8]
Financial Instruments, Owned, at Fair Value			72,585,000	[7],[8]
2.42%, due 11/1/2042(a)(b) | Fannie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount			75,395,000	[7],[8]
Financial Instruments, Owned, at Fair Value			78,710,000	[7],[8]
2.43%, due 2/1/2043(b) | Fannie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount			25,000,000	[7]
Financial Instruments, Owned, at Fair Value			26,174,000	[7]
2.44%, due 7/1/2042 - 10/1/2042(a)(b) | Fannie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount			241,204,000	[7],[8]
Financial Instruments, Owned, at Fair Value			251,833,000	[7],[8]
2.45%, due 10/1/2042 - 11/1/2042(b) | Fannie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount			87,021,000	[7]
Financial Instruments, Owned, at Fair Value			90,808,000	[7]
2.46%, due 6/1/2042(a)(b) | Fannie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount			57,508,000	[7],[8]
Financial Instruments, Owned, at Fair Value			60,021,000	[7],[8]
2.50%, due 2/1/2028 - 3/1/2028 | Fannie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount			1,900,000,000
Financial Instruments, Owned, at Fair Value			1,985,203,000
2.51%, due 10/1/2042(a)(b) | Fannie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount			146,723,000	[7],[8]
Financial Instruments, Owned, at Fair Value			153,519,000	[7],[8]
2.57%, due 7/1/2042 - 2/1/2043(a)(b) | Fannie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount			130,372,000	[7],[8]
Financial Instruments, Owned, at Fair Value			136,513,000	[7],[8]
2.60%, due 2/1/2043(b) | Fannie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount			50,000,000	[7]
Financial Instruments, Owned, at Fair Value			52,406,000	[7]
2.62%, due 7/1/2042(a)(b) | Fannie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount			46,138,000	[7],[8]
Financial Instruments, Owned, at Fair Value			48,256,000	[7],[8]
2.63%, due 4/1/2042(a)(b) | Fannie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount			35,609,000	[7],[8]
Financial Instruments, Owned, at Fair Value			37,264,000	[7],[8]
2.79%, due 1/1/2042 - 3/1/2042(a)(b) | Fannie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount			85,732,000	[7],[8]
Financial Instruments, Owned, at Fair Value			89,912,000	[7],[8]
2.80%, due 2/1/2042 - 11/1/2042(a)(b) | Fannie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount			349,671,000	[7],[8]
Financial Instruments, Owned, at Fair Value			366,718,000	[7],[8]
2.81%, due 2/1/2042(a)(b) | Fannie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount			55,367,000	[7],[8]
Financial Instruments, Owned, at Fair Value			58,090,000	[7],[8]
2.84%, due 2/1/2042(a)(b) | Fannie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount			32,607,000	[7],[8]
Financial Instruments, Owned, at Fair Value			34,247,000	[7],[8]
2.85%, due 12/1/2041(a)(b) | Fannie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount			53,238,000	[7],[8]
Financial Instruments, Owned, at Fair Value			55,952,000	[7],[8]
2.87%, due 1/1/2042(a)(b) | Fannie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount			59,639,000	[7],[8]
Financial Instruments, Owned, at Fair Value			63,234,000	[7],[8]
2.89%, due 2/1/2042(a)(b) | Fannie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount			40,377,000	[7],[8]
Financial Instruments, Owned, at Fair Value			42,409,000	[7],[8]
3.00%, due 1/1/2041(a)(b) | Fannie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount			29,557,000	[7],[8]
Financial Instruments, Owned, at Fair Value			31,002,000	[7],[8]
3.00%, due 2/1/2027 - 12/1/2027(a) | Fannie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount			6,794,861,000	[8]
Financial Instruments, Owned, at Fair Value			7,183,772,000	[8]
3.00%, due 2/1/2032 - 2/1/2033(a) | Fannie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount			967,503,000	[8]
Financial Instruments, Owned, at Fair Value			1,018,411,000	[8]
3.02%, due 12/1/2040(a)(b) | Fannie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount			101,591,000	[7],[8]
Financial Instruments, Owned, at Fair Value			106,680,000	[7],[8]
3.04%, due 9/1/2041(a)(b) | Fannie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount			38,752,000	[7],[8]
Financial Instruments, Owned, at Fair Value			40,639,000	[7],[8]
3.05%, due 9/1/2041(a)(b) | Fannie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount			36,363,000	[7],[8]
Financial Instruments, Owned, at Fair Value			38,205,000	[7],[8]
3.06%, due 6/1/2042(b) | Fannie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount			37,791,000	[7]
Financial Instruments, Owned, at Fair Value			40,031,000	[7]
3.16%, due 9/1/2041(a)(b) | Fannie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount			31,611,000	[7],[8]
Financial Instruments, Owned, at Fair Value			33,343,000	[7],[8]
3.18%, due 11/1/2041(a)(b) | Fannie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount			27,672,000	[7],[8]
Financial Instruments, Owned, at Fair Value			29,179,000	[7],[8]
3.21%, due 9/1/2041(a)(b) | Fannie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount			84,111,000	[7],[8]
Financial Instruments, Owned, at Fair Value			88,670,000	[7],[8]
3.26%, due 4/1/2041(a)(b) | Fannie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount			38,941,000	[7],[8]
Financial Instruments, Owned, at Fair Value			40,970,000	[7],[8]
3.30%, due 5/1/2041(a)(b) | Fannie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount			31,843,000	[7],[8]
Financial Instruments, Owned, at Fair Value			33,499,000	[7],[8]
3.35%, due 8/1/2041(a)(b) | Fannie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount			27,024,000	[7],[8]
Financial Instruments, Owned, at Fair Value			28,827,000	[7],[8]
3.36%, due 6/1/2041(a)(b) | Fannie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount			81,763,000	[7],[8]
Financial Instruments, Owned, at Fair Value			86,263,000	[7],[8]
3.38%, due 5/1/2041(a)(b) | Fannie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount			17,894,000	[7],[8]
Financial Instruments, Owned, at Fair Value			18,822,000	[7],[8]
3.50%, due 7/1/2021(a) | Fannie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount			207,091,000	[8]
Financial Instruments, Owned, at Fair Value			219,747,000	[8]
3.50%, due 12/1/2025 - 2/1/2028(a) | Fannie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount			1,481,478,000	[8]
Financial Instruments, Owned, at Fair Value			1,572,774,000	[8]
3.50%, due 8/1/2042 - 3/1/2043(a) | Fannie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount			3,209,041,000	[8]
Financial Instruments, Owned, at Fair Value			3,425,338,000	[8]
3.61%, due 6/1/2041(a)(b) | Fannie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount			49,197,000	[7],[8]
Financial Instruments, Owned, at Fair Value			52,170,000	[7],[8]
3.65%, due 7/1/2040(a)(b) | Fannie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount			29,174,000	[7],[8]
Financial Instruments, Owned, at Fair Value			30,810,000	[7],[8]
3.99%, due 9/1/2039(b) | Fannie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount			11,717,000	[7]
Financial Instruments, Owned, at Fair Value			12,432,000	[7]
4.00%, due 1/1/2025 - 6/1/2026(a) | Fannie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount			613,772,000	[8]
Financial Instruments, Owned, at Fair Value			657,599,000	[8]
4.00%, due 8/1/2042(a) | Fannie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount			106,594,000	[8]
Financial Instruments, Owned, at Fair Value			114,664,000	[8]
4.50%, due 2/1/2028 - 11/1/2030(a) | Fannie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount			136,333,000	[8]
Financial Instruments, Owned, at Fair Value			147,730,000	[8]
4.50%, due 11/1/2041(a) | Fannie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount			256,057,000	[8]
Financial Instruments, Owned, at Fair Value			277,486,000	[8]
2.30%, due 11/1/2042(a)(b) | Federal Home Loan Mortgage Corporation Certificates and Obligations (FHLMC) [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount			99,093,000	[7],[8]
Financial Instruments, Owned, at Fair Value			103,022,000	[7],[8]
2.52%, due 9/1/2042(a)(b) | Federal Home Loan Mortgage Corporation Certificates and Obligations (FHLMC) [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount			122,825,000	[7],[8]
Financial Instruments, Owned, at Fair Value			128,547,000	[7],[8]
2.55%, due 11/1/2042(b) | Federal Home Loan Mortgage Corporation Certificates and Obligations (FHLMC) [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount			54,278,000	[7]
Financial Instruments, Owned, at Fair Value			56,826,000	[7]
3.27%, due 6/1/2041(a)(b) | Federal Home Loan Mortgage Corporation Certificates and Obligations (FHLMC) [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount			32,330,000	[7],[8]
Financial Instruments, Owned, at Fair Value			33,995,000	[7],[8]
3.30%, due 1/1/2041(a)(b) | Federal Home Loan Mortgage Corporation Certificates and Obligations (FHLMC) [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount			35,460,000	[7],[8]
Financial Instruments, Owned, at Fair Value			37,608,000	[7],[8]
3.50%, due 4/1/2026 - 2/1/2027(a) | Federal Home Loan Mortgage Corporation Certificates and Obligations (FHLMC) [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount			187,349,000	[8]
Financial Instruments, Owned, at Fair Value			197,014,000	[8]
3.63%, due 6/1/2041(a)(b) | Federal Home Loan Mortgage Corporation Certificates and Obligations (FHLMC) [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount			32,394,000	[7],[8]
Financial Instruments, Owned, at Fair Value			34,105,000	[7],[8]
4.50%, due 12/1/2024 - 5/1/2025(a) | Federal Home Loan Mortgage Corporation Certificates and Obligations (FHLMC) [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount			52,637,000	[8]
Financial Instruments, Owned, at Fair Value			56,006,000	[8]
4.00%, due 1/20/2040(a)(b) | Ginnie Mae Pools [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount			12,875,000	[7],[8]
Financial Instruments, Owned, at Fair Value			13,818,000	[7],[8]
0.06%, due 2/7/2013(a)(d) | US Treasury Bill [Member]
Investment Holdings [Line Items]
Debt Instrument, Face Amount			38,000,000	[12],[8]
Financial Instruments, Owned, at Fair Value			37,999,000	[12],[8]
12/30/2014 | Interest Rate Cap Contracts [Member]
Investment Holdings [Line Items]
Financial Instruments, Owned, at Fair Value			38,000
Derivative, Notional Amount			200,000,000
7/16/2022 | Interest Rate Cap Contracts [Member]
Investment Holdings [Line Items]
Financial Instruments, Owned, at Fair Value			36,010,000
Derivative, Notional Amount			500,000,000
7/25/2022 | Interest Rate Cap Contracts [Member]
Investment Holdings [Line Items]
Financial Instruments, Owned, at Fair Value			36,880,000
Derivative, Notional Amount			500,000,000
5/26/2013 | Interest Rate Swap [Member]
Investment Holdings [Line Items]
Financial Instruments, Owned, at Fair Value			-529,000
Derivative, Notional Amount			100,000,000
Derivative, Fixed Interest Rate			1.60%
6/28/2013 | Interest Rate Swap [Member]
Investment Holdings [Line Items]
Financial Instruments, Owned, at Fair Value			-1,574,000
Derivative, Notional Amount			300,000,000
Derivative, Fixed Interest Rate			1.38%
7/15/2013 | Interest Rate Swap [Member]
Investment Holdings [Line Items]
Financial Instruments, Owned, at Fair Value			-1,706,000
Derivative, Notional Amount			300,000,000
Derivative, Fixed Interest Rate			1.37%
12/15/2013 | Interest Rate Swap [Member]
Investment Holdings [Line Items]
Financial Instruments, Owned, at Fair Value			-3,773,000
Derivative, Notional Amount			400,000,000
Derivative, Fixed Interest Rate			1.31%
12/16/2013 | Interest Rate Swap [Member]
Investment Holdings [Line Items]
Financial Instruments, Owned, at Fair Value			-3,602,000
Derivative, Notional Amount			400,000,000
Derivative, Fixed Interest Rate			1.26%
12/16/2013 | Interest Rate Swap [Member]
Investment Holdings [Line Items]
Financial Instruments, Owned, at Fair Value			-4,581,000
Derivative, Notional Amount			500,000,000
Derivative, Fixed Interest Rate			1.28%
12/17/2013 | Interest Rate Swap [Member]
Investment Holdings [Line Items]
Financial Instruments, Owned, at Fair Value			-3,838,000
Derivative, Notional Amount			400,000,000
Derivative, Fixed Interest Rate			1.32%
9/6/2017 | Interest Rate Swap [Member]
Investment Holdings [Line Items]
Financial Instruments, Owned, at Fair Value			26,000
Derivative, Notional Amount			250,000,000
Derivative, Fixed Interest Rate			0.77%
9/6/2017 | Interest Rate Swap [Member]
Investment Holdings [Line Items]
Financial Instruments, Owned, at Fair Value			-243,000
Derivative, Notional Amount			$500,000,000
Derivative, Fixed Interest Rate			0.77%
[1]	Derived from audited financial statements.
[2]	Percentage of net assets.
[3]	Comprised of investments that were individually less than 1% of net assets.
[4]	The Companybs interest rate swap contracts receive a floating rate set quarterly to three month LIBOR. Interest rate caps will receive a floating rate quarterly in the amount of three month LIBOR that is in excess of the cap rate.
[5]	Securities or a portion of the securities are pledged as collateral for repurchase agreements, interest rate swap contracts, or forward settling transactions.
[6]	The coupon rate shown on floating or adjustable rate securities represents the rate at SeptemberB 30, 2013.
[7]	The coupon rate shown on floating or adjustable rate securities represents the rate at DecemberB 31, 2012.
[8]	rived from audited financial statements.(a)Securities or a portion of the securities are pledged as collateral for repurchase agreements, interest rate swa
[9]	The interest rate swap effective date is AprilB 24, 2013, and it does not accrue any income or expense until that date.
[10]	The interest rate swap effective date is November 29, 2013, and it does not accrue any income or expense until that date.
[11]	The interest rate swap effective date is April 25, 2014, and it does not accrue any income or expense until that date.
[12]	Zero coupon bond, rate shown represents purchase yield.

Condensed_Statements_Of_Operat

Condensed Statements Of Operations (USD $)	3 Months Ended				9 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012
INVESTMENT INCOME:
Interest income from Agency RMBS	$85,599		$75,609		$238,691		$210,108
Other income	37		1,022		1,597		3,639
Total investment income	85,636		76,631		240,288		213,747
EXPENSES:
Interest	11,969		11,893		41,047		27,739
Compensation and benefits	3,453		3,068		10,198		9,578
General, administrative and other	2,144		2,272		6,623		6,160
Total expenses	17,566		17,233		57,868		43,477
Net investment income	68,070		59,398		182,420		170,270
GAINS AND (LOSSES) FROM INVESTMENTS:
Net realized gain (loss) on investments	-407,728		27,049		-572,466		93,335
Net unrealized appreciation (depreciation) on investments	423,509		194,078		-146,859		229,528
Net gain (loss) from investments	15,781		221,127		-719,325		322,863
GAINS AND (LOSSES) FROM SWAP AND CAP CONTRACTS:
Net swap and cap interest income (expense)	-23,744		-17,255		-72,399		-41,448
Net gain (loss) on termination of swap and cap contracts	25,707		0		41,666		0
Net unrealized appreciation (depreciation) on swap and cap contracts	-55,243		-21,363		183,720		-38,955
Net gain (loss) from swap and cap contracts	-53,280	[1]	-38,618	[1]	152,987	[1]	-80,403	[1]
Net income (loss)	30,571		241,907		-383,918		412,730
DIVIDENDS ON PREFERRED STOCK	5,203		953		10,651		953
NET INCOME (LOSS) AVAILABLE TO COMMON SHARES	$25,368		$240,954		($394,569)		$411,777
NET INCOME (LOSS) PER COMMON SHARE BASIC & DILUTED	$0.14		$1.46		($2.29)		$3.19
[1]	See Note 2 for additional information on the Companybs purpose for entering into interest rate swaps and caps and the decision not to designate them as hedging instruments.

Condensed_Statement_Of_Changes

Condensed Statement Of Changes In Net Assets (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013		Sep. 30, 2013
Net income (loss):
Net investment income	$68,070		$182,420
Net realized gain (loss) on investments	-407,728		-572,466
Net unrealized appreciation (depreciation) on investments	423,509		-146,859
Net gain (loss) from swap and cap contracts	-53,280	[1]	152,987	[1]
Net income (loss)	30,571		-383,918
Dividends on preferred stock	-5,203		-10,651
Net income (loss) available to common shares	25,368		-394,569
Capital transactions:
Net proceeds (payments) from issues and repurchase of common shares	46,100		72,772
Stock Issued During Period, Value, Other	0		193,550
Distributions to common stockholders	-56,739		-171,357
Amortization of share based compensation	905		2,573
Increase(Decrease) in net assets from capital transactions	-101,934		-48,006
Total decrease in net assets	-76,566		-442,575
Net assets:
Beginning of period	2,036,653		2,402,662	[2]
End of period	$1,960,087		$1,960,087
[1]	See Note 2 for additional information on the Companybs purpose for entering into interest rate swaps and caps and the decision not to designate them as hedging instruments.
[2]	Derived from audited financial statements.

Condensed_Statements_Of_Cash_F

Condensed Statements Of Cash Flows (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013		Sep. 30, 2012
Document Period End Date	30-Sep-13
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income (loss)	($383,918)		$412,730
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Purchase of investment securities	-39,821,249		-26,295,320
Premium paid on interest rate caps	-91,860		-133,483
Proceeds from disposition of investment securities	43,280,830		11,428,649
Proceeds from termination of interest rate swap and cap contracts	103,275		0
Proceeds from paydowns of investment securities	2,122,423		1,940,265
Amortization of share based compensation	2,573		2,119
Amortization of premiums and discounts on investment securities	104,137		69,092
Amortization of premiums on interest rate cap contracts	17,985		7,412
Net realized (gain) loss on investments	572,466		-93,335
Net (gain) loss on termination of cap contracts	-37,958		0
Net unrealized (appreciation) depreciation on investments	146,859		-229,528
Net unrealized (appreciation) depreciation on swap and cap contracts	-183,720		38,955
Change in assets and liabilities:
Receivable for securities sold and principal repayments	-734,148		-14,873
Interest receivable	7,785		-22,618
Other assets	-66		-39
Payable for securities purchased	-2,858,777		5,620,745
Payable for cash received as collateral	6,578		47,960
Accrued interest payable	-13,724		3,772
Accrued expenses and other liabilities	4,784		3,216
Net cash provided by (used in) operating activities	2,244,275		-7,214,281
Proceeds from repurchase agreements	99,827,406		59,689,598
Repayments of repurchase agreements	-102,073,642		-53,658,435
Net proceeds (payments) from issuance and repurchase of common shares	-72,772		1,235,842
Net proceeds from issuance of preferred stock	193,550		72,488
Distributions paid	-122,102		-116,224
Net cash provided by (used in) financing activities	-2,247,560		7,223,269
Net increase (decrease) in cash and cash equivalents	-3,285		8,988
CASH AND CASH EQUIVALENTS - Beginning of period	13,882	[1]	11,508
CASH AND CASH EQUIVALENTS - End of period	10,597		20,496
SUPPLEMENTAL DISCLOSURES OF CASH FLOW INFORMATION:
Interest paid	116,079		67,128
SUPPLEMENTAL DISCLOSURES OF NONCASH FLOW INFORMATION:
Distributions declared, not yet paid	61,149		79,677
Reinvestment of common share distributions	$0		$1,310
[1]	Derived from audited financial statements.

Orginazation

Orginazation	9 Months Ended
	Sep. 30, 2013
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization	ORGANIZATION
	CYS Investments, Inc. (the “Company”) was formed as a Maryland corporation on January 3, 2006, and commenced operations on February 10, 2006. The Company has elected to be taxed and intends to continue to qualify as a real estate investment trust (“REIT”) and is required to comply with the provisions of the Internal Revenue Code of 1986, as amended (the “Code”), with respect thereto. Since March 2008, the Company has primarily purchased residential mortgage-backed securities that are issued and the principal and interest of which are guaranteed by a federally chartered corporation (“Agency RMBS”), such as the Federal National Mortgage Association (“Fannie Mae”) or the Federal Home Loan Mortgage Corporation (“Freddie Mac”), or an agency of the U.S. government such as the Government National Mortgage Association (“Ginnie Mae”), or debt securities issued by the United States Department of Treasury ("U.S. Treasury Securities"). On December 10, 2012 the Company's board of directors amended and restated its investment guidelines to permit the company to invest in (i) Agency RMBS, (ii) collateralized mortgage obligations issued by a government agency or government-sponsored entity that are collateralized by Agency RMBS and (iii) U.S. Treasury Securities or, a government sponsored entity that is not backed by collateral but, in the case of government agencies, is backed by the full faith and credit of the U.S. government, and, in the case of government sponsored entities, is backed by the integrity and creditworthiness of the issuer (“US Agency Debentures”). The Company’s common stock, Series A Cumulative Redeemable Preferred Stock, $25.00 liquidation preference (the "Series A Preferred Stock"), and Series B Cumulative Redeemable Preferred Stock, $25.00 liquidation preference (the "Series B Preferred Stock"), trade on the New York Stock Exchange under the symbols “CYS,” "CYS PrA" and "CYS PrB," respectively.

Significant_Accounting_Policie

Significant Accounting Policies (Notes)	9 Months Ended
	Sep. 30, 2013
Accounting Policies [Abstract]
Significant Accounting Policies	SIGNIFICANT ACCOUNTING POLICIES
	Basis of Presentation
	The accompanying interim unaudited condensed financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”) and the instructions to Form 10-Q and Article 10, Rule 10-01 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements. In the opinion of management, all adjustments (consisting of normal recurring accruals) considered necessary for a fair presentation have been included. The interim unaudited condensed financial statements should be read in conjunction with the Company’s audited financial statements as of and for the year ended December 31, 2012, included in its annual report on Form 10-K. The results for interim periods are not necessarily indicative of the results to be expected for the fiscal year.
	The Company adopted Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (“ASC”) 946, Clarification of the Scope of Audit and Accounting Guide Investment Companies (“ASC 946”), prior to its deferral in February 2008. Under ASC 946, the Company uses financial reporting for investment companies.
	Segment Reporting
	The Company operates as a single segment reporting to the Chief Executive Officer, who manages the entire investment portfolio.
	Use of Estimates
	The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. Actual results could differ from those management estimates.
	Cash and Cash Equivalents
	Cash and cash equivalents include cash on hand, cash held in banks and highly liquid investments with original maturities of three months or less. Interest income earned on cash and cash equivalents is recorded in other income.
	Offsetting
	The Company’s derivative agreements and repurchase agreements generally contain provisions that allow for netting or the offsetting of receivables and payables with each counterparty. The Company reports amounts in the statement of assets and liabilities on a gross basis without regard for such rights of offset or master netting arrangements. The Company's repurchase agreements are fully collateralized and do not require further disclosure in accordance with ASC 210-20 Balance Sheet Offsetting. As of September 30, 2013, the Company recorded $267.4 million of derivative assets on the statement of assets and liabilities, of which $19.2 million could be offset in the event of default under master netting arrangements. As a result of this amount subject to potential offsetting and the $226.8 million of collateral posted in support of the Company’s derivative assets, $21.4 million of derivative assets were exposed to counterparty credit risk. All derivative liabilities at September 30, 2013 were fully collateralized. As of December 31, 2012, the Company recorded $124.2 million of derivative assets on the statement of assets and liabilities, of which $34.1 million could be offset in the event of default under master netting arrangements. As a result of this amount subject to potential offsetting and the $47.3 million of collateral posted in support of the Company’s derivative assets, $42.8 million of derivative assets were exposed to counterparty credit risk. All derivative liabilities at December 31, 2012 were fully collateralized.
	Interest Rate Swap and Cap Contracts
	The Company utilizes interest rate swaps and caps to hedge the interest rate risk associated with the financing of its portfolio. Specifically, the Company seeks to hedge the exposure to potential interest rate mismatches between the interest earned on investments and the borrowing costs caused by fluctuations in short term interest rates. In a simple interest rate swap, one investor pays a floating rate of interest on a notional principal amount and receives a fixed rate of interest on the same notional principal amount for a specified period of time. Alternatively, an investor may pay a fixed rate and receive a floating rate. In a simple interest rate cap, one investor pays a premium for a notional principal amount based on a capped interest rate (the “cap rate”). If the floating interest rate (the “floating rate”) exceeds the cap rate, the investor receives a payment from the cap counterparty equal to the difference between the floating rate and the cap rate on the same notional principal amount for a specified period of time. Alternatively, an investor may receive a premium and pay the difference in cap rate and floating rate.
	During the term of the interest rate swap or cap, the Company makes or receives periodic payments and unrealized gains or losses are recorded as a result of marking the swap and cap to their fair value. When the swap or cap is terminated, the Company records a realized gain or loss equal to the difference between the proceeds from (or cost of) the closing transaction and the Company’s cost basis in the contract, if any. The periodic payments, amortization of premiums on cap contracts and any realized or unrealized gains or losses are reported under gains and losses from swap and cap contracts in the statements of operations. Swaps involve a risk that interest rates will move contrary to the Company’s expectations, thereby increasing the Company’s payment obligation.
	Because the Company uses financial reporting for investment companies, its investments, including its interest rate swap and cap contracts, are carried at fair value with changes in fair value included in earnings. Consequently, there would be no impact to designating interest rate swaps and caps as cash flow or fair value hedges under GAAP.
	The Company's interest rate swap and cap contracts are subject to master netting arrangements. The Company is exposed to credit loss in the event of nonperformance by the counterparty to the swap or cap limited to the fair value of collateral posted in excess of the fair value of the contract in a net liability position and the shortage of the fair value of collateral posted for the contract in a net asset position. As of September 30, 2013 and December 31, 2012, the Company did not anticipate nonperformance by any counterparty. Should interest rates move unexpectedly, the Company may not achieve the anticipated benefits of the interest rate swap or cap and may realize a loss.
	Investment Valuation
	The Company has established a pricing committee responsible for establishing valuation policies and procedures as well as approving valuations on a monthly basis at a pricing meeting. The pricing committee is made up of individuals from the accounting team, the investment team and senior management.
	Agency RMBS, Agency Debentures and U.S. Treasury Securities are generally valued on the basis of valuations provided by third party pricing services, as derived from such services’ pricing models. Inputs to the models may include, but are not limited to, reported trades, executable bid and asked prices, broker quotations, prices or yields of securities with similar characteristics, benchmark curves or information pertaining to the issuer, as well as industry and economic events. The pricing services may use a matrix approach, which considers information regarding securities with similar characteristics to determine the valuation for a security.
	Interest rate swaps and caps are generally valued using valuations provided by broker quotations. Such broker quotations are based on the present value of fixed and projected floating rate cash flows over the term of the swap contract. Future cash flows are discounted to their present value using swap rates provided by electronic data services or by broker. No credit valuation adjustments were made in determining the fair value of the Company's interest rate swaps and caps.
	Fair values of long-lived assets, including real estate, are primarily derived internally and are based on inputs observed from sales transactions for similar assets. For real estate, fair values are based on discounted cash flow estimates which reflect current and projected lease profiles and available industry information about capitalization rates and expected trends in rents and occupancy.
	All valuations received from third party pricing services or broker quotes are non-binding. To date, the Company has not adjusted any of the prices received from third party pricing services or brokers, and all prices are reviewed by the Company. This review includes comparisons of similar market transactions, alternative third party pricing services and broker quotes, or comparisons to a pricing model. To ensure the proper fair value hierarchy, the Company reviews the third party pricing service’s methodology to understand whether observable or unobservable inputs are being used.
	Agency RMBS
	The Company’s investments in Agency RMBS consist of pass-through certificates backed by fixed rate, monthly reset adjustable-rate loans (“ARMs”) and hybrid ARMs, the principal and interest of which are guaranteed by Fannie Mae, Freddie Mac or Ginnie Mae. Hybrid ARMs have interest rates that have an initial fixed period (typically three, five, seven or ten years) and thereafter reset at regular intervals in a manner similar to ARMs.
	Forward Settling Transactions
	The Company engages in forward settling transactions to purchase certain securities. The Company records forward settling transactions on the trade date and maintains security positions such that sufficient liquid assets will be available to make payment on the settlement date for the securities purchased. Securities purchased on a forward settling basis are carried at fair value and only begin earning interest on the settlement date. Losses may occur on these transactions due to changes in market conditions or the failure of counterparties to perform under the contract. Among other forward settling transactions, the Company from time to time transacts in to-be-announced securities (“TBAs”). As with other forward settling transactions, a seller agrees to issue TBAs at a future date. However, the seller does not specify the particular securities to be delivered. Instead, the Company agrees to accept any security that meets specified terms such as issuer, interest rate and terms of underlying mortgages. The Company records TBAs on the trade date utilizing information associated with the specified terms of the transaction as opposed to the specific mortgages. TBAs are carried at fair value and begin earning interest on the settlement date. Losses may occur due to the fact that the actual underlying mortgages received may be less favorable than those anticipated by the Company.
	As of September 30, 2013, the Company received Agency RMBS, U.S. Treasury Securities and cash with a fair value of $5.4 million on its open forward settling transactions. As of December 31, 2012, the Company pledged Agency RMBS, U.S. Treasury Securities and cash with a fair value of $10.4 million on its open forward settling transactions.
	Repurchase Agreements
	Repurchase agreements are borrowings that are collateralized by the Company’s Agency RMBS and are carried at their amortized cost, which approximates their fair value due to their short term nature, generally 30-90 days. The Company’s repurchase agreement counterparties are large institutional dealers in fixed income securities. Collateral is valued daily and counterparties may require additional collateral when the fair value of the collateral declines. Counterparties have the right to sell or repledge collateral pledged for repurchase agreements.
	Investment Transactions and Income
	The Company records its transactions in securities on a trade date basis. Realized gains and losses on securities transactions are recorded on an identified cost basis. Interest income and expense are recorded on the accrual basis. Interest income on Agency RMBS and Agency Debentures is accrued based on outstanding principal amount of the securities and their contractual terms. Amortization of premium and accretion of discount are recorded using the yield to maturity method, and are included in investment income in the statements of operations. The Company does not estimate prepayments when calculating the yield to maturity on Agency RMBS. The amount of premium or discount associated with a prepayment is recorded through investment income on the statements of operations as they occur.
	Interest on collateralized loan obligations ("CLOs") is accrued at a rate determined based on estimated future cash flows and adjusted prospectively as future cash flow amounts are recast. For CLOs placed on nonaccrual status or when the Company cannot reliably estimate cash flows, the cost recovery method is used.
	Compensation and Benefits
	Included in the Company’s compensation and benefits are salaries, incentive compensation, benefits, share based compensation and the expense relating to restricted stock granted to non-employees (prior to the internalization of the Company's management, which became effective on September 1, 2011). The Company accounts for share based compensation using the fair value based methodology prescribed by ASC 718, Share-Based Payment (“ASC 718”). Compensation cost related to restricted common stock issued is measured at its estimated fair value at the grant date and recognized as expense over the vesting period.
	Income Taxes
	The Company has elected to be taxed as a REIT and intends to continue to comply with provisions of the Code with respect thereto. As a REIT, the Company generally will not be subject to federal or state income tax on income that it currently distributes to its stockholders. To maintain its qualification as a REIT, the Company must distribute at least 90% of its REIT taxable income to its stockholders and meet certain other tests relating to assets and income.
	Earnings Per Share (“EPS”)
	Basic EPS is computed using the two class method by dividing net income (loss), after adjusting for the impact of unvested stock awards deemed to be participating securities, by the weighted average number of common shares outstanding calculated excluding unvested stock awards. Diluted EPS is computed by dividing net income (loss), after adjusting for the impact of unvested stock awards deemed to be participating securities, by the weighted average number of common shares outstanding calculated excluding unvested stock awards, giving effect to common stock options and warrants, if they are not anti-dilutive. See Note 3 for EPS computations.
	Recent Accounting Pronouncements
	In June 2013, the FASB issued ASU 2013-08, Financial Services-Investment Companies (Topic 946). This update modifies the guidance for Topic 946 for determining whether an entity is an investment company for GAAP purposes. It requires entities that adopted Statement of Position 07-1 prior to its deferral to reassess whether they continue to meet the definition of an investment company for GAAP purposes. The guidance is effective for interim and annual reporting periods in fiscal years that begin after December 15, 2013, with retrospective application. Earlier application is prohibited. Management has performed its reassessment and has determined that the Company does not meet the definition of an investment company in accordance with ASC 946 and as a result will need to select and apply other appropriate accounting principles which will change the presentation of the Company's financial statements effective January 1, 2014. Management is still assessing the impact on the Company's financial statements and currently does not expect there will be a material effect on the Company's financial position or results of operations.
	In January 2013, the FASB issued ASU 2013-01, Clarifying the Scope of Disclosures about Offsetting Assets and Liabilities (Topic 210), Balance Sheet. The update addresses implementation issues about ASU 2011-11 and applies to derivatives accounted for in accordance with Topic 815, Derivatives and Hedging, including bifurcated embedded derivatives, repurchase agreements and reverse repurchase agreements, and securities borrowing and securities lending transactions that are either offset in accordance with ASC 210-20-45 or ASC 815-10-45 or subject to an enforceable master netting arrangement or similar agreement. The guidance was effective January 1, 2013 and was applied retrospectively. This guidance does not amend the circumstances in which the Company offsets its derivative positions. As a result, the guidance does not have a material effect on the Company's financial statements.

Earnings_Per_Share_Notes

Earnings Per Share (Notes)	9 Months Ended
	Sep. 30, 2013
Earnings Per Share [Abstract]
Earnings Per Share [Text Block]	EARNINGS PER SHARE
	Components of the computation of basic and diluted EPS were as follows (in thousands except per share numbers):
		Three Months Ended September 30,						Nine Months Ended September 30,
		2013			2012			2013			2012
	Net income (loss)	$	30,571		$	241,907		$	(383,918	)	$	412,730
	Less preferred stock dividends	(5,203		)	(953		)	(10,651		)	(953		)
	Net income (loss) available to common shares	25,368			240,954			(394,569		)	411,777
	Less dividends paid:
	Common shares	(56,444		)	(78,397		)	(170,473		)	(195,175		)
	Unvested shares	(295		)	(327		)	(884		)	(1,083		)
	Undistributed earnings (loss)	(31,371		)	162,230			(565,926		)	215,519
	Basic weighted average shares outstanding:
	Common shares	169,465			164,269			172,284			128,116
	Basic earnings (loss) per common share:
	Distributed earnings	$	0.33		$	0.48		$	0.99		$	1.52
	Undistributed earnings (loss)	(0.19		)	0.98			(3.28		)	1.67
	Basic earnings (loss) per common share	$	0.14		$	1.46		$	(2.29	)	$	3.19
	Diluted weighted average shares outstanding:
	Common shares	169,465			164,269			172,284			128,116
	Net effect of dilutive stock options (1)	—			—			—			—
		169,465			164,269			172,284			128,116
	Diluted earnings (loss) per common share:
	Distributed earnings	$	0.33		$	0.48		$	0.99		$	1.52
	Undistributed earnings (loss)	(0.19		)	0.98			(3.28		)	1.67
	Diluted earnings (loss) per common share	$	0.14		$	1.46		$	(2.29	)	$	3.19
	__________________
	(1)For the three and nine months ended September 30, 2013 and 2012, the Company had an aggregate of 131 stock options outstanding with a weighted average exercise price of $30.00 that were not included in the calculation of EPS, as their inclusion would have been anti-dilutive. These instruments may have a dilutive impact on future EPS.

Investments_In_Securities_And_

Investments In Securities And Interest Rate Swap And Cap Contracts (Notes)	9 Months Ended
	Sep. 30, 2013
Derivative, Fair Value, Net [Abstract]
Investments In Securities And Interest Rate Swap And Cap Contracts	INVESTMENTS IN SECURITIES AND INTEREST RATE SWAP AND CAP CONTRACTS AND OTHER ASSETS
	The Company’s valuation techniques are based on observable and unobservable inputs. Observable inputs reflect readily obtainable data from independent sources, while unobservable inputs reflect the Company’s market assumptions. ASC 820, Fair Value Measurements, classifies these inputs into the following hierarchy:
	Level 1 Inputs—Quoted prices for identical instruments in active markets.
	Level 2 Inputs—Quoted prices for similar instruments in active markets; quoted prices for identical or similar instruments in markets that are not active; and model-derived valuations whose inputs are observable or whose significant value drivers are observable.
	Level 3 Inputs—Instruments with primarily unobservable value drivers.
	Excluded from the tables below are financial instruments carried on the accompanying financial statements at cost basis, which is deemed to approximate fair value, primarily due to the short duration of these instruments, including cash and cash equivalents, receivables, payables and borrowings under repurchase arrangements with initial terms of 1 year or less. The fair value of these instruments is determined using level two inputs. The following tables provide a summary of the Company’s assets and liabilities that are measured at fair value on a recurring basis as of September 30, 2013 and December 31, 2012:
	September 30, 2013	Fair Value Measurements Using
		Level 1				Level 2				Level 3				Total
		(in thousands)
	Assets
	Agency RMBS	$	—			$	14,449,307			$	—			$	14,449,307
	Other Investments	—				—				6,945				6,945
	Derivative assets	—				267,409				—				267,409
	Total	$	—			$	14,716,716			$	6,945			$	14,723,661
	Liabilities
	Derivative liabilities	$	—			$	49,537			$	—			$	49,537
	December 31, 2012	Fair Value Measurements Using
		Level 1				Level 2				Level 3				Total
		(in thousands)
	Assets
	Agency RMBS	$	—			$	20,804,143			$	—			$	20,804,143
	U.S. Treasury Bills	37,999				—				—				37,999
	Other Investments	—				—				19,576				19,576
	Derivative assets	—				124,169				—				124,169
	Total	$	37,999			$	20,928,312			$	19,576			$	20,985,887
	Liabilities
	Derivative liabilities	$	—			$	98,575			$	—			$	98,575
	Other Investments is comprised of CLOs and real estate assets. The table below presents a reconciliation of changes in other investments classified as Level 3 in the Company’s financial statements for the three and nine months ended September 30, 2013 and 2012. CLOs were generally valued using valuations provided by broker quotations. The Company validated the broker quotations using internal discounted cash flow models. The significant unobservable inputs used in the fair value measurement of the Company’s CLOs were prepayment rates, probability of default, and recovery rate in the event of default. Significant changes in any of those inputs in isolation would have resulted in a materially different fair value measurement. Generally, a change in the assumption used for the probability of default is accompanied by a directionally similar change in the assumption used for the loss severity upon default and a directionally opposite change in the assumption used for prepayment rates. The Company did not own any CLOs as of September 30, 2013. The weighted average inputs to the models as of December 31, 2012 were:
		Constant			Default Rate			Recovery Rate			Recovery Lag
		Prepayment Rate
	31-Dec-12	20	%		2	%		69	%		6 Months
	Fair values of real estate assets are valued based on discounted cash flow models. A discussion of the method of fair valuing these assets is included above in Note 2 “Investment Valuation.” The significant unobservable input used in the fair value measurement is capitalization rates, which the Company estimated to be between 4% and 5% at September 30, 2013 and December 31, 2012.
	Level 3 Fair Value Reconciliation
	(In thousands)	Three Months Ended September 30,								Nine Months Ended September 30,
	Other investments	2013				2012				2013				2012
	Beginning balance level 3 assets	$	6,945			$	24,802			$	19,576			$	18,675
	Cash payments recorded as a reduction of cost basis	—				(964		)		(324		)		(3,081		)
	Change in net unrealized appreciation (depreciation)	—				1,483				(6,721		)		2,799
	Net purchases (sales)	—				(8,592		)		(12,005		)		(1,664		)
	Net gain (loss) on sales	—				2,648				6,419				2,648
	Transfers into (out of) level 3	—				—				—				—
	Ending balance level 3 assets	$	6,945			$	19,377			$	6,945			$	19,377
	The Agency RMBS portfolio consisted of Agency RMBS as follows:
	September 30, 2013		Face Value				Fair Value				Weighted Average
	Asset Type		(in thousands)								Cost/Face				Fair Value/Face				MTR(1)	Coupon		CPR(2)
	15 Year Fixed Rate		$	5,995,535			$	6,240,505			$	102.43			$	104.09			N/A	3.14	%	15.1	%
	20 Year Fixed Rate		89,615				96,644				103.08				107.84				N/A	4.5	%	31.3	%
	30 Year Fixed Rate		5,813,529				5,985,741				102.33				102.96				N/A	3.7	%	4.1	%
	Hybrid ARMs		2,088,601				2,126,417				103.59				101.81				68.9	2.57	%	19.1	%
	Total/Weighted Average		$	13,987,280			$	14,449,307			$	102.57			$	103.3				3.3	%	12.4	%
	December 31, 2012
	10 Year Fixed Rate		$	207,091			$	219,747			$	103.6			$	106.11			N/A	3.5	%	19.4	%
	15 Year Fixed Rate		11,092,374				11,717,136				104.32				105.63				N/A	3.05	%	16.1	%
	20 Year Fixed Rate		1,087,835				1,148,932				104.96				105.62				N/A	3.17	%	10.1	%
	30 Year Fixed Rate		3,571,692				3,817,488				105.78				106.88				N/A	3.59	%	8.9	%
	Hybrid ARMs		3,722,510				3,900,840				103.54				104.79				74.3	2.71	%	19.1	%
	Total/Weighted Average		$	19,681,502			$	20,804,143			$	104.47			$	105.7				3.1	%	15.8	%
	__________________
	(1)	MTR, or “Months to Reset” is the weighted average number of months remaining before the fixed rate on a hybrid ARM becomes a variable rate. At the end of the fixed period, the variable rate will be determined by the margin and the pre-specified caps of the ARM. After the fixed period, 100% of the hybrid ARMs in the portfolio reset annually.
	(2)	CPR, or “Constant Prepayment Rate,” is a method of expressing the prepayment rate for a mortgage pool that assumes that a constant fraction of the remaining principal is prepaid each month or year. Specifically, the CPR is an annualized version of the prior three month prepayment rate. Securities with no prepayment history are excluded from this calculation.
	As of September 30, 2013 and December 31, 2012, the Company’s Agency RMBS were purchased at a net premium to their face value with approximately $366.0 million and $879.6 million, respectively, of unamortized premium included in their cost basis. The premium purchase price is due to the average coupon interest rates on these investments being higher than prevailing market rates.
	Actual maturities of Agency RMBS are generally shorter than stated contractual maturities (which range up to 30 years), as they are affected by the contractual lives of the underlying mortgages, periodic payments and prepayments of principal. As of September 30, 2013 and December 31, 2012, the average final contractual maturity of the Company’s Agency RMBS portfolio is in year 2036 and 2033, respectively.
	In order to mitigate its interest rate exposure, the Company enters into interest rate swap and cap contracts. The Company had the following activity in interest rate swap and cap transactions during the three and nine months ended September 30, 2013 and 2012 (in thousands):
	Three and Nine Months Ended September 30, 2013							Three and Nine Months Ended September 30, 2012
Trade Date	Transaction		Notional				Trade Date	Transaction		Notional
Feb-13	Opened		$	1,500,000			Apr-12	Opened		$	500,000
Mar-13	Terminated		(500,000		)		May-12	Opened		600,000
Mar-13	Opened		1,200,000				Jun-12	Opened		600,000
Apr-13	Opened		500,000				Jul-12	Opened		2,250,000
May-13	Opened		500,000				Sep-12	Opened		1,000,000
May-13	Matured		(100,000		)		Net Increase			$	4,950,000
Jun-13	Terminated		(700,000		)
Jun-13	Matured		(300,000		)
Jul-13	Matured		(300,000		)
Aug-13	Terminated		(2,200,000		)
Aug-13	Opened		500,000
Net Increase			$	100,000
As of September 30, 2013 and December 31, 2012, the Company had pledged Agency RMBS and U.S Treasury Securities with a fair value of $92.3 million and $127.6 million, respectively, as collateral on interest rate swap and cap contracts. As of September 30, 2013 the Company had Agency RMBS and U.S. Treasury Securities of $199.5 million and cash of $32.7 million pledged to it as collateral for its interest rate swap and cap contracts. As of December 31, 2012 the Company had Agency RMBS and U.S. Treasury Securities of $18.4 million and cash of $28.9 million pledged to it as collateral for its interest rate cap contracts. Below is a summary of our interest rate swap and cap contracts open as of September 30, 2013 and December 31, 2012 and the net gain and loss on swap and cap contracts for the three and nine months ended September 30, 2013 and 2012 (in thousands):
Derivatives not designated as hedging instruments under ASC 815(a)
Interest Rate Swap Contracts	Notional Amount				Fair Value				Statement of Assets and Liabilities Location
September 30, 2013	$	3,340,000			$	(49,537	)		Derivative liabilities, at fair value
September 30, 2013	3,750,000				51,417				Derivative assets, at fair value
December 31, 2012	6,490,000				(98,575		)		Derivative liabilities, at fair value
December 31, 2012	1,000,000				1,180				Derivative assets, at fair value
Interest Rate Cap Contracts	Notional Amount				Fair Value				Statement of Assets and Liabilities Location
September 30, 2013	$	3,900,000			$	215,992			Derivative assets, at fair value
December 31, 2012	3,400,000				122,989				Derivative assets, at fair value
				Amount of Gain or (Loss) Recognized in Income on Derivatives
Derivatives Not Designated as Hedging Instruments Under ASC 815(a)		Location of Gain or (Loss) Recognized in Income on Derivative		Three Months Ended September 30,								Nine Months Ended September 30,
				2013				2012				2013				2012
Interest rate swap and cap contracts		Net gain (loss) from swap and cap contracts		$	(53,280	)		$	(38,618	)		$	152,987			$	(80,403	)
__________________
(a)	See Note 2 for additional information on the Company’s purpose for entering into interest rate swaps and caps and the decision not to designate them as hedging instruments.
Credit Risk
At September 30, 2013 and December 31, 2012, the Company continued to have minimal exposure to credit losses on its mortgage assets by owning principally Agency RMBS. The payment of principal and interest on Agency RMBS is guaranteed by Freddie Mac, Fannie Mae or Ginnie Mae. In September 2008, both Freddie Mac and Fannie Mae were placed in the conservatorship of the United States government.
On August 5, 2011, Standard & Poor’s downgraded the U.S.’s credit rating to AA+ for the first time. Because Fannie Mae and Freddie Mac are in conservatorship of the U.S. government, the implied credit ratings of Agency RMBS guaranteed by Freddie Mac, Fannie Mae or Ginnie Mae were also downgraded to AA+. While this downgrade did not have a significant impact on the fair value of the Agency RMBS in the Company’s portfolio, it has increased the uncertainty regarding the credit risk of Agency RMBS.

Borrowings_Notes

Borrowings (Notes)	9 Months Ended
	Sep. 30, 2013
Short-term Debt [Abstract]
Borrowings	BORROWINGS
	The Company leverages its Agency RMBS portfolio through the use of repurchase agreements. Each of the borrowing vehicles used by the Company bears interest at floating rates based on a spread above or below the LIBOR. The fair value of borrowings under repurchase agreements approximates their carrying amount due to the short term nature of these financial instruments.
	Certain information with respect to the Company’s borrowings is summarized in the following tables. Each of the borrowings listed is contractually due in one year or less (dollars in thousands).
	September 30, 2013
	Outstanding repurchase agreements	$	11,735,071
	Interest accrued thereon	$	2,865
	Weighted average borrowing rate	0.39		%
	Weighted average remaining maturity (in days)	44
	Fair value of the collateral(1)	$	12,342,112
	December 31, 2012
	Outstanding repurchase agreements	$	13,981,307
	Interest accrued thereon	$	11,717
	Weighted average borrowing rate	0.48		%
	Weighted average remaining maturity (in days)	19.6
	Fair value of the collateral(1)	$	14,693,645
	__________________
	-1	Collateral for repurchase agreements consisted of Agency RMBS and U.S. Treasury Securities.
	At September 30, 2013 and December 31, 2012, the Company did not have any borrowings under repurchase agreements where the amount at risk with an individual counterparty exceeded 10% of net assets.

Contingencies_Notes

Contingencies (Notes)	9 Months Ended
	Sep. 30, 2013
Commitments and Contingencies Disclosure [Abstract]
Contingencies	COMMITMENTS AND CONTINGENCIES
	The Company enters into certain contracts that contain a variety of indemnifications, principally with broker dealers. As of September 30, 2013 and December 31, 2012, no claims have been asserted under these indemnification agreements. Accordingly, the Company has no liabilities recorded for these agreements as of September 30, 2013 and December 31, 2012.

Share_Capital_Notes

Share Capital (Notes)	9 Months Ended
	Sep. 30, 2013
Stockholders' Equity Note [Abstract]
Stockholders' Equity Note Disclosure [Text Block]	SHARE CAPITAL
	The Company has authorized 500,000,000 shares of common stock having par value of $0.01 per share. As of September 30, 2013 and December 31, 2012, the Company had issued and outstanding 166,880,305 and 174,924,149 shares of common stock, respectively. The Company’s common stock transactions during the nine months ended September 30, 2013 and 2012 are as follows (in thousands):
		Nine Months Ended September 30, 2013					Nine Months Ended September 30, 2012
		Shares		Amount			Shares		Amount
	Shares sold in public offerings or issued as restricted stock	351		$	2,364		92,104		$	1,238,141
	Shares issued in reinvestment of distributions	—		—			98		1,310
	Shares repurchased or canceled	(8,395	)	(72,563		)	(13	)	(180		)
	Net increase (decrease)	(8,044	)	$	(70,199	)	92,189		$	1,239,271
	The Company has authorized 50,000,000 shares of preferred stock having a par value of $0.01 per share. As of September 30, 2013 and December 31, 2012, 3,000,000 shares of 7.75% Series A Preferred Stock ($25.00 liquidation preference) were issued and outstanding. As of September 30, 2013, 8,000,000 shares of 7.50% Series B Preferred Stock ($25.00 liquidation preference) were issued and outstanding. The Series A Preferred Stock and Series B Preferred Stock will not be redeemable before August 3, 2017 and April 30, 2018, respectively, except under circumstances where it is necessary to preserve the Company's qualification as a REIT, for federal income tax purposes or the occurrence of a change of control. On or after August 3, 2017 and April 30, 2018, the Company may, at its option, redeem any or all of the shares of the Series A Preferred Stock and Series B Preferred Stock, respectively, at $25.00 per share plus any accumulated and unpaid dividends to, but not including, the respective redemption date. The Series A Preferred Stock and Series B Preferred Stock have no stated maturity and are not subject to any sinking fund or mandatory redemption.
	Equity Offerings
	On February 1, 2012, the Company closed a public offering of 28,750,000 shares of its common stock at a public offering price of $13.28 per share for total net proceeds of approximately $377.3 million, after the underwriting discount and commissions and expenses.
	On July 16, 2012, the Company closed a public offering of 46,000,000 shares of its common stock at a public offering price of $13.70 per share for total net proceeds of approximately $622.2 million, after the underwriting discount and commissions and expenses.
	On August 3, 2012, the Company closed a public offering of 3,000,000 shares of its Series A Preferred Stock, liquidation preference of $25.00 per share, for total net proceeds of approximately $72.4 million, after the underwriting discount and commissions and expenses.
	On April 30, 2013, the Company closed a public offering of 8,000,000 shares of its Series B Preferred Stock, liquidation preference of $25.00 per share, for total net proceeds of approximately $193.6 million, after the underwriting discount and commissions and expenses.
	Dividend Reinvestment and Direct Stock Purchase Plan (“DSPP”)
	The Company sponsors a dividend reinvestment and direct stock purchase plan through which stockholders may purchase additional shares of common stock by reinvesting some or all of the cash dividends received on shares of common stock.
	Stockholders may also make optional cash purchases of shares of common stock subject to certain limitations detailed in the plan prospectus. For the nine months ended September 30, 2013 the Company did not issue any shares under the plan. For the nine months ended September 30, 2012, the Company issued 5.3 million shares under the plan raising approximately $74.0 million of net proceeds. As of September 30, 2013 and December 31, 2012, there were approximately 4.1 million shares available for issuance under the plan.
	Restricted Stock Awards
	For the nine months ended September 30, 2013 and 2012, the Company granted 350,807 and 205,390 shares of restricted stock, respectively, to certain of its directors, officers and employees.
	Equity Placement Program (“EPP”)
	On June 7, 2011, the Company entered into a sales agreement with JMP Securities LLC whereby the Company may, from time to time, publicly offer and sell up to 15.0 million shares of the Company’s common stock through at-the-market transactions and/or privately negotiated transactions. For the nine months ended September 30, 2013, the Company did not issue any shares under the plan. For the nine months ended September 30, 2012, the Company issued 11.9 million shares under the plan raising approximately $164.3 million. As of September 30, 2013 and December 31, 2012, approximately 3.1 million shares of common stock remained available for issuance and sale under the sales agreement.
	Share Repurchase Program
	On November 15, 2012, the Company announced that its board of directors had authorized the repurchase of shares of the Company’s common stock having an aggregate value of up to $250 million. For the nine months ended September 30, 2013, the Company repurchased 8.4 million shares with a weighted average purchase price of $8.62 or approximately $72.4 million in the aggregate. The Company did not make any repurchases during 2012.

Financial_Highlights_Notes

Financial Highlights (Notes)	9 Months Ended
	Sep. 30, 2013
Financial Highlights [Abstract]
Financial Highlights	FINANCIAL HIGHLIGHTS
	In accordance with financial reporting requirements applicable to investment companies, the Company has included below certain financial highlight information for the three and nine months ended September 30, 2013 and 2012:
		Per Common Share
		Three Months Ended September 30,								Nine Months Ended September 30,
		2013				2012				2013				2012
	Net asset value, beginning of period	$	10.2			$	13.52			$	13.31			$	13.02
	Net income (loss):
	Net investment income	0.4			(a)	0.36			(a)	1.05			(a)	1.32			(a)
	Net gain (loss) from investments and swap and cap contracts	(0.22		)	(a)	1.11			(a)	(3.27		)	(a)	1.88			(a)
	Net income (loss)	0.18				1.47				(2.22		)		3.2
	Dividends on preferred stock	(0.03		)	(a)	(0.01		)	(a)	(0.06		)	(a)	(0.01		)	(a)
	Net income (loss) available to common shares	0.15				1.46				(2.28		)		3.19
	Capital transactions:
	Distributions to common stockholders	(0.34		)		(0.45		)		(1.00		)		(1.45		)
	Issuance/Repurchase of common and preferred shares and amortization of share based compensation	0.09			(a)	(0.07		)	(a)	0.07			(a)	(0.30		)	(a)
	Net decrease in net asset value from capital transactions	(0.25		)		(0.52		)		(0.93		)		(1.75		)
	Net asset value, end of period	$	10.1			$	14.46			$	10.1			$	14.46
	Net asset value total return (%)	2.35		%	(b)	10.28		%	(b)	(16.60		)%	(b)	22.2		%	(b)
	Market value total return (%)	(8.02		)%	(b)	5.59		%	(b)	(23.53		)%	(b)	18.88		%	(b)
	Ratios to Average Net Assets
	Expenses before interest expense	1.13		%	(c)	0.93		%	(c)	1.01		%	(c)	1.16		%	(c)
	Total expenses	3.55		%	(c)	3		%	(c)	3.47		%	(c)	3.21		%	(c)
	Net investment income	13.77		%	(c)	10.33		%	(c)	10.92		%	(c)	12.59		%	(c)
	__________________
	(a)	Calculated based on average shares outstanding during the period. Average shares outstanding include vested and unvested restricted shares and differs from weighted average shares outstanding used in calculating EPS (see Note 3).
	(b)	Not computed on an annualized basis.
	(c)	Computed on an annualized basis.

Subsequent_Events_Notes

Subsequent Events (Notes)	9 Months Ended
	Sep. 30, 2013
Subsequent Events [Abstract]
Subsequent Events	SUBSEQUENT EVENTS
	On October 1, 2013, an aggregate of 13,937 shares of restricted common stock were granted to certain directors as a portion of their compensation for serving on the Company’s board of directors.
	The CPR of the Company’s Agency RMBS portfolio was approximately 5.5% for the month of October 2013.

Significant_Accounting_Policie1

Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2013
Accounting Policies [Abstract]
Basis Of Presentation	Basis of Presentation
	The accompanying interim unaudited condensed financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”) and the instructions to Form 10-Q and Article 10, Rule 10-01 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements. In the opinion of management, all adjustments (consisting of normal recurring accruals) considered necessary for a fair presentation have been included. The interim unaudited condensed financial statements should be read in conjunction with the Company’s audited financial statements as of and for the year ended December 31, 2012, included in its annual report on Form 10-K. The results for interim periods are not necessarily indicative of the results to be expected for the fiscal year.
	The Company adopted Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (“ASC”) 946, Clarification of the Scope of Audit and Accounting Guide Investment Companies (“ASC 946”), prior to its deferral in February 2008. Under ASC 946, the Company uses financial reporting for investment companies.
Segment Reporting	Segment Reporting
	The Company operates as a single segment reporting to the Chief Executive Officer, who manages the entire investment portfolio.
Use Of Estimates	Use of Estimates
	The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. Actual results could differ from those management estimates.
Cash And Cash Equivalents	Cash and Cash Equivalents
	Cash and cash equivalents include cash on hand, cash held in banks and highly liquid investments with original maturities of three months or less. Interest income earned on cash and cash equivalents is recorded in other income.
Offsetting Assets [Table Text Block]	Offsetting
	The Company’s derivative agreements and repurchase agreements generally contain provisions that allow for netting or the offsetting of receivables and payables with each counterparty. The Company reports amounts in the statement of assets and liabilities on a gross basis without regard for such rights of offset or master netting arrangements. The Company's repurchase agreements are fully collateralized and do not require further disclosure in accordance with ASC 210-20 Balance Sheet Offsetting. As of September 30, 2013, the Company recorded $267.4 million of derivative assets on the statement of assets and liabilities, of which $19.2 million could be offset in the event of default under master netting arrangements. As a result of this amount subject to potential offsetting and the $226.8 million of collateral posted in support of the Company’s derivative assets, $21.4 million of derivative assets were exposed to counterparty credit risk. All derivative liabilities at September 30, 2013 were fully collateralized. As of December 31, 2012, the Company recorded $124.2 million of derivative assets on the statement of assets and liabilities, of which $34.1 million could be offset in the event of default under master netting arrangements. As a result of this amount subject to potential offsetting and the $47.3 million of collateral posted in support of the Company’s derivative assets, $42.8 million of derivative assets were exposed to counterparty credit risk.
Interest Rate Swap And Cap Contracts	Interest Rate Swap and Cap Contracts
	The Company utilizes interest rate swaps and caps to hedge the interest rate risk associated with the financing of its portfolio. Specifically, the Company seeks to hedge the exposure to potential interest rate mismatches between the interest earned on investments and the borrowing costs caused by fluctuations in short term interest rates. In a simple interest rate swap, one investor pays a floating rate of interest on a notional principal amount and receives a fixed rate of interest on the same notional principal amount for a specified period of time. Alternatively, an investor may pay a fixed rate and receive a floating rate. In a simple interest rate cap, one investor pays a premium for a notional principal amount based on a capped interest rate (the “cap rate”). If the floating interest rate (the “floating rate”) exceeds the cap rate, the investor receives a payment from the cap counterparty equal to the difference between the floating rate and the cap rate on the same notional principal amount for a specified period of time. Alternatively, an investor may receive a premium and pay the difference in cap rate and floating rate.
	During the term of the interest rate swap or cap, the Company makes or receives periodic payments and unrealized gains or losses are recorded as a result of marking the swap and cap to their fair value. When the swap or cap is terminated, the Company records a realized gain or loss equal to the difference between the proceeds from (or cost of) the closing transaction and the Company’s cost basis in the contract, if any. The periodic payments, amortization of premiums on cap contracts and any realized or unrealized gains or losses are reported under gains and losses from swap and cap contracts in the statements of operations. Swaps involve a risk that interest rates will move contrary to the Company’s expectations, thereby increasing the Company’s payment obligation.
	Because the Company uses financial reporting for investment companies, its investments, including its interest rate swap and cap contracts, are carried at fair value with changes in fair value included in earnings. Consequently, there would be no impact to designating interest rate swaps and caps as cash flow or fair value hedges under GAAP.
	The Company's interest rate swap and cap contracts are subject to master netting arrangements. The Company is exposed to credit loss in the event of nonperformance by the counterparty to the swap or cap limited to the fair value of collateral posted in excess of the fair value of the contract in a net liability position and the shortage of the fair value of collateral posted for the contract in a net asset position. As of September 30, 2013 and December 31, 2012, the Company did not anticipate nonperformance by any counterparty. Should interest rates move unexpectedly, the Company may not achieve the anticipated benefits of the interest rate swap or cap and may realize a loss.
Investment Valuation	Investment Valuation
	The Company has established a pricing committee responsible for establishing valuation policies and procedures as well as approving valuations on a monthly basis at a pricing meeting. The pricing committee is made up of individuals from the accounting team, the investment team and senior management.
	Agency RMBS, Agency Debentures and U.S. Treasury Securities are generally valued on the basis of valuations provided by third party pricing services, as derived from such services’ pricing models. Inputs to the models may include, but are not limited to, reported trades, executable bid and asked prices, broker quotations, prices or yields of securities with similar characteristics, benchmark curves or information pertaining to the issuer, as well as industry and economic events. The pricing services may use a matrix approach, which considers information regarding securities with similar characteristics to determine the valuation for a security.
	Interest rate swaps and caps are generally valued using valuations provided by broker quotations. Such broker quotations are based on the present value of fixed and projected floating rate cash flows over the term of the swap contract. Future cash flows are discounted to their present value using swap rates provided by electronic data services or by broker. No credit valuation adjustments were made in determining the fair value of the Company's interest rate swaps and caps.
	Fair values of long-lived assets, including real estate, are primarily derived internally and are based on inputs observed from sales transactions for similar assets. For real estate, fair values are based on discounted cash flow estimates which reflect current and projected lease profiles and available industry information about capitalization rates and expected trends in rents and occupancy.
	All valuations received from third party pricing services or broker quotes are non-binding. To date, the Company has not adjusted any of the prices received from third party pricing services or brokers, and all prices are reviewed by the Company. This review includes comparisons of similar market transactions, alternative third party pricing services and broker quotes, or comparisons to a pricing model. To ensure the proper fair value hierarchy, the Company reviews the third party pricing service’s methodology to understand whether observable or unobservable inputs are being used.
Agency RMBS	Agency RMBS
	The Company’s investments in Agency RMBS consist of pass-through certificates backed by fixed rate, monthly reset adjustable-rate loans (“ARMs”) and hybrid ARMs, the principal and interest of which are guaranteed by Fannie Mae, Freddie Mac or Ginnie Mae. Hybrid ARMs have interest rates that have an initial fixed period (typically three, five, seven or ten years) and thereafter reset at regular intervals in a manner similar to ARMs.
Forward Settling Transactions	Forward Settling Transactions
	The Company engages in forward settling transactions to purchase certain securities. The Company records forward settling transactions on the trade date and maintains security positions such that sufficient liquid assets will be available to make payment on the settlement date for the securities purchased. Securities purchased on a forward settling basis are carried at fair value and only begin earning interest on the settlement date. Losses may occur on these transactions due to changes in market conditions or the failure of counterparties to perform under the contract. Among other forward settling transactions, the Company from time to time transacts in to-be-announced securities (“TBAs”). As with other forward settling transactions, a seller agrees to issue TBAs at a future date. However, the seller does not specify the particular securities to be delivered. Instead, the Company agrees to accept any security that meets specified terms such as issuer, interest rate and terms of underlying mortgages. The Company records TBAs on the trade date utilizing information associated with the specified terms of the transaction as opposed to the specific mortgages. TBAs are carried at fair value and begin earning interest on the settlement date. Losses may occur due to the fact that the actual underlying mortgages received may be less favorable than those anticipated by the Company.
	As of September 30, 2013, the Company received Agency RMBS, U.S. Treasury Securities and cash with a fair value of $5.4 million on its open forward settling transactions. As of December 31, 2012, the Company pledged Agency RMBS, U.S. Treasury Securities and cash with a fair value of $10.4 million on its open forward settling transactions.
Repurchase Agreements	Repurchase Agreements
	Repurchase agreements are borrowings that are collateralized by the Company’s Agency RMBS and are carried at their amortized cost, which approximates their fair value due to their short term nature, generally 30-90 days. The Company’s repurchase agreement counterparties are large institutional dealers in fixed income securities. Collateral is valued daily and counterparties may require additional collateral when the fair value of the collateral declines. Counterparties have the right to sell or repledge collateral pledged for repurchase agreements.
Investment Transactions And Income	Investment Transactions and Income
	The Company records its transactions in securities on a trade date basis. Realized gains and losses on securities transactions are recorded on an identified cost basis. Interest income and expense are recorded on the accrual basis. Interest income on Agency RMBS and Agency Debentures is accrued based on outstanding principal amount of the securities and their contractual terms. Amortization of premium and accretion of discount are recorded using the yield to maturity method, and are included in investment income in the statements of operations. The Company does not estimate prepayments when calculating the yield to maturity on Agency RMBS. The amount of premium or discount associated with a prepayment is recorded through investment income on the statements of operations as they occur.
	Interest on collateralized loan obligations ("CLOs") is accrued at a rate determined based on estimated future cash flows and adjusted prospectively as future cash flow amounts are recast. For CLOs placed on nonaccrual status or when the Company cannot reliably estimate cash flows, the cost recovery method is used.
Compensation And Benefits	Compensation and Benefits
	Included in the Company’s compensation and benefits are salaries, incentive compensation, benefits, share based compensation and the expense relating to restricted stock granted to non-employees (prior to the internalization of the Company's management, which became effective on September 1, 2011). The Company accounts for share based compensation using the fair value based methodology prescribed by ASC 718, Share-Based Payment (“ASC 718”). Compensation cost related to restricted common stock issued is measured at its estimated fair value at the grant date and recognized as expense over the vesting period.
Income Taxes	Income Taxes
	The Company has elected to be taxed as a REIT and intends to continue to comply with provisions of the Code with respect thereto. As a REIT, the Company generally will not be subject to federal or state income tax on income that it currently distributes to its stockholders. To maintain its qualification as a REIT, the Company must distribute at least 90% of its REIT taxable income to its stockholders and meet certain other tests relating to assets and income.
Earnings Per Share ("EPS")	Earnings Per Share (“EPS”)
	Basic EPS is computed using the two class method by dividing net income (loss), after adjusting for the impact of unvested stock awards deemed to be participating securities, by the weighted average number of common shares outstanding calculated excluding unvested stock awards. Diluted EPS is computed by dividing net income (loss), after adjusting for the impact of unvested stock awards deemed to be participating securities, by the weighted average number of common shares outstanding calculated excluding unvested stock awards, giving effect to common stock options and warrants, if they are not anti-dilutive. See Note 3 for EPS computations.
Description of New Accounting Pronouncements Not yet Adopted	Recent Accounting Pronouncements
	In June 2013, the FASB issued ASU 2013-08, Financial Services-Investment Companies (Topic 946). This update modifies the guidance for Topic 946 for determining whether an entity is an investment company for GAAP purposes. It requires entities that adopted Statement of Position 07-1 prior to its deferral to reassess whether they continue to meet the definition of an investment company for GAAP purposes. The guidance is effective for interim and annual reporting periods in fiscal years that begin after December 15, 2013, with retrospective application. Earlier application is prohibited. Management has performed its reassessment and has determined that the Company does not meet the definition of an investment company in accordance with ASC 946 and as a result will need to select and apply other appropriate accounting principles which will change the presentation of the Company's financial statements effective January 1, 2014. Management is still assessing the impact on the Company's financial statements and currently does not expect there will be a material effect on the Company's financial position or results of operations.
	In January 2013, the FASB issued ASU 2013-01, Clarifying the Scope of Disclosures about Offsetting Assets and Liabilities (Topic 210), Balance Sheet. The update addresses implementation issues about ASU 2011-11 and applies to derivatives accounted for in accordance with Topic 815, Derivatives and Hedging, including bifurcated embedded derivatives, repurchase agreements and reverse repurchase agreements, and securities borrowing and securities lending transactions that are either offset in accordance with ASC 210-20-45 or ASC 815-10-45 or subject to an enforceable master netting arrangement or similar agreement. The guidance was effective January 1, 2013 and was applied retrospectively. This guidance does not amend the circumstances in which the Company offsets its derivative positions. As a result, the guidance does not have a material effect on the Company's financial statements.

Earnings_Per_Share_Tables

Earnings Per Share (Tables)	9 Months Ended
	Sep. 30, 2013
Earnings Per Share [Abstract]
Schedule Of Computation Of Basic And Diluted Earnings Per Share	Components of the computation of basic and diluted EPS were as follows (in thousands except per share numbers):
		Three Months Ended September 30,						Nine Months Ended September 30,
		2013			2012			2013			2012
	Net income (loss)	$	30,571		$	241,907		$	(383,918	)	$	412,730
	Less preferred stock dividends	(5,203		)	(953		)	(10,651		)	(953		)
	Net income (loss) available to common shares	25,368			240,954			(394,569		)	411,777
	Less dividends paid:
	Common shares	(56,444		)	(78,397		)	(170,473		)	(195,175		)
	Unvested shares	(295		)	(327		)	(884		)	(1,083		)
	Undistributed earnings (loss)	(31,371		)	162,230			(565,926		)	215,519
	Basic weighted average shares outstanding:
	Common shares	169,465			164,269			172,284			128,116
	Basic earnings (loss) per common share:
	Distributed earnings	$	0.33		$	0.48		$	0.99		$	1.52
	Undistributed earnings (loss)	(0.19		)	0.98			(3.28		)	1.67
	Basic earnings (loss) per common share	$	0.14		$	1.46		$	(2.29	)	$	3.19
	Diluted weighted average shares outstanding:
	Common shares	169,465			164,269			172,284			128,116
	Net effect of dilutive stock options (1)	—			—			—			—
		169,465			164,269			172,284			128,116
	Diluted earnings (loss) per common share:
	Distributed earnings	$	0.33		$	0.48		$	0.99		$	1.52
	Undistributed earnings (loss)	(0.19		)	0.98			(3.28		)	1.67
	Diluted earnings (loss) per common share	$	0.14		$	1.46		$	(2.29	)	$	3.19
	__________________
	(1)For the three and nine months ended September 30, 2013 and 2012, the Company had an aggregate of 131 stock options outstanding with a weighted average exercise price of $30.00 that were not included in the calculation of EPS, as their inclusion would have been anti-dilutive. These instruments may have a dilutive impact on future EPS.

Investments_In_Securities_And_1

Investments In Securities And Interest Rate Swap And Cap Contracts (Tables)	9 Months Ended
	Sep. 30, 2013
Derivative, Fair Value, Net [Abstract]
Assets And Liabilities Measured At Fair Value On A Recurring Basis	The following tables provide a summary of the Company’s assets and liabilities that are measured at fair value on a recurring basis as of September 30, 2013 and December 31, 2012:
	September 30, 2013	Fair Value Measurements Using
		Level 1				Level 2				Level 3				Total
		(in thousands)
	Assets
	Agency RMBS	$	—			$	14,449,307			$	—			$	14,449,307
	Other Investments	—				—				6,945				6,945
	Derivative assets	—				267,409				—				267,409
	Total	$	—			$	14,716,716			$	6,945			$	14,723,661
	Liabilities
	Derivative liabilities	$	—			$	49,537			$	—			$	49,537
	December 31, 2012	Fair Value Measurements Using
		Level 1				Level 2				Level 3				Total
		(in thousands)
	Assets
	Agency RMBS	$	—			$	20,804,143			$	—			$	20,804,143
	U.S. Treasury Bills	37,999				—				—				37,999
	Other Investments	—				—				19,576				19,576
	Derivative assets	—				124,169				—				124,169
	Total	$	37,999			$	20,928,312			$	19,576			$	20,985,887
	Liabilities
	Derivative liabilities	$	—			$	98,575			$	—			$	98,575
Summary Of The Weighted Average Inputs To The Models	The weighted average inputs to the models as of December 31, 2012 were:
		Constant			Default Rate			Recovery Rate			Recovery Lag
		Prepayment Rate
	31-Dec-12	20	%		2	%		69	%		6 Months
Schedule Of Fair Value Reconciliation, Level 3	Level 3 Fair Value Reconciliation
	(In thousands)	Three Months Ended September 30,								Nine Months Ended September 30,
	Other investments	2013				2012				2013				2012
	Beginning balance level 3 assets	$	6,945			$	24,802			$	19,576			$	18,675
	Cash payments recorded as a reduction of cost basis	—				(964		)		(324		)		(3,081		)
	Change in net unrealized appreciation (depreciation)	—				1,483				(6,721		)		2,799
	Net purchases (sales)	—				(8,592		)		(12,005		)		(1,664		)
	Net gain (loss) on sales	—				2,648				6,419				2,648
	Transfers into (out of) level 3	—				—				—				—
	Ending balance level 3 assets	$	6,945			$	19,377			$	6,945			$	19,377
Agency RMBS Portfolio	The Agency RMBS portfolio consisted of Agency RMBS as follows:
	September 30, 2013		Face Value				Fair Value				Weighted Average
	Asset Type		(in thousands)								Cost/Face				Fair Value/Face				MTR(1)	Coupon		CPR(2)
	15 Year Fixed Rate		$	5,995,535			$	6,240,505			$	102.43			$	104.09			N/A	3.14	%	15.1	%
	20 Year Fixed Rate		89,615				96,644				103.08				107.84				N/A	4.5	%	31.3	%
	30 Year Fixed Rate		5,813,529				5,985,741				102.33				102.96				N/A	3.7	%	4.1	%
	Hybrid ARMs		2,088,601				2,126,417				103.59				101.81				68.9	2.57	%	19.1	%
	Total/Weighted Average		$	13,987,280			$	14,449,307			$	102.57			$	103.3				3.3	%	12.4	%
	December 31, 2012
	10 Year Fixed Rate		$	207,091			$	219,747			$	103.6			$	106.11			N/A	3.5	%	19.4	%
	15 Year Fixed Rate		11,092,374				11,717,136				104.32				105.63				N/A	3.05	%	16.1	%
	20 Year Fixed Rate		1,087,835				1,148,932				104.96				105.62				N/A	3.17	%	10.1	%
	30 Year Fixed Rate		3,571,692				3,817,488				105.78				106.88				N/A	3.59	%	8.9	%
	Hybrid ARMs		3,722,510				3,900,840				103.54				104.79				74.3	2.71	%	19.1	%
	Total/Weighted Average		$	19,681,502			$	20,804,143			$	104.47			$	105.7				3.1	%	15.8	%
	__________________
	(1)	MTR, or “Months to Reset” is the weighted average number of months remaining before the fixed rate on a hybrid ARM becomes a variable rate. At the end of the fixed period, the variable rate will be determined by the margin and the pre-specified caps of the ARM. After the fixed period, 100% of the hybrid ARMs in the portfolio reset annually.
	(2)	CPR, or “Constant Prepayment Rate,” is a method of expressing the prepayment rate for a mortgage pool that assumes that a constant fraction of the remaining principal is prepaid each month or year. Specifically, the CPR is an annualized version of the prior three month prepayment rate. Securities with no prepayment history are excluded from this calculation.
Summary Of Interest Rate Swap And Cap Contracts	In order to mitigate its interest rate exposure, the Company enters into interest rate swap and cap contracts. The Company had the following activity in interest rate swap and cap transactions during the three and nine months ended September 30, 2013 and 2012 (in thousands):
	Three and Nine Months Ended September 30, 2013							Three and Nine Months Ended September 30, 2012
	Trade Date	Transaction		Notional				Trade Date	Transaction		Notional
	Feb-13	Opened		$	1,500,000			Apr-12	Opened		$	500,000
	Mar-13	Terminated		(500,000		)		May-12	Opened		600,000
	Mar-13	Opened		1,200,000				Jun-12	Opened		600,000
	Apr-13	Opened		500,000				Jul-12	Opened		2,250,000
	May-13	Opened		500,000				Sep-12	Opened		1,000,000
	May-13	Matured		(100,000		)		Net Increase			$	4,950,000
	Jun-13	Terminated		(700,000		)
	Jun-13	Matured		(300,000		)
	Jul-13	Matured		(300,000		)
	Aug-13	Terminated		(2,200,000		)
	Aug-13	Opened		500,000
	Net Increase			$	100,000
	As of September 30, 2013 and December 31, 2012, the Company had pledged Agency RMBS and U.S Treasury Securities with a fair value of $92.3 million and $127.6 million, respectively, as collateral on interest rate swap and cap contracts. As of September 30, 2013 the Company had Agency RMBS and U.S. Treasury Securities of $199.5 million and cash of $32.7 million pledged to it as collateral for its interest rate swap and cap contracts. As of December 31, 2012 the Company had Agency RMBS and U.S. Treasury Securities of $18.4 million and cash of $28.9 million pledged to it as collateral for its interest rate cap contracts.
Schedule Of Notional Amount And Fair Value Of Derivatives	elow is a summary of our interest rate swap and cap contracts open as of September 30, 2013 and December 31, 2012 and the net gain and loss on swap and cap contracts for the three and nine months ended September 30, 2013 and 2012 (in thousands):
	Derivatives not designated as hedging instruments under ASC 815(a)
	Interest Rate Swap Contracts	Notional Amount				Fair Value				Statement of Assets and Liabilities Location
	September 30, 2013	$	3,340,000			$	(49,537	)		Derivative liabilities, at fair value
	September 30, 2013	3,750,000				51,417				Derivative assets, at fair value
	December 31, 2012	6,490,000				(98,575		)		Derivative liabilities, at fair value
	December 31, 2012	1,000,000				1,180				Derivative assets, at fair value
	Interest Rate Cap Contracts	Notional Amount				Fair Value				Statement of Assets and Liabilities Location
	September 30, 2013	$	3,900,000			$	215,992			Derivative assets, at fair value
	December 31, 2012	3,400,000				122,989				Derivative assets, at fair value
					Amount of Gain or (Loss) Recognized in Income on Derivatives
	Derivatives Not Designated as Hedging Instruments Under ASC 815(a)		Location of Gain or (Loss) Recognized in Income on Derivative		Three Months Ended September 30,								Nine Months Ended September 30,
					2013				2012				2013				2012
	Interest rate swap and cap contracts		Net gain (loss) from swap and cap contracts		$	(53,280	)		$	(38,618	)		$	152,987			$	(80,403	)
	__________________
	(a)	See Note 2 for additional information on the Company’s purpose for entering into interest rate swaps and caps and the decision not to designate them as hedging instruments.
	C

Borrowings_Tables

Borrowings (Tables)	9 Months Ended
	Sep. 30, 2013
Short-term Debt [Abstract]
Schedule Of Company's Borrowings	Certain information with respect to the Company’s borrowings is summarized in the following tables. Each of the borrowings listed is contractually due in one year or less (dollars in thousands).
	September 30, 2013
	Outstanding repurchase agreements	$	11,735,071
	Interest accrued thereon	$	2,865
	Weighted average borrowing rate	0.39		%
	Weighted average remaining maturity (in days)	44
	Fair value of the collateral(1)	$	12,342,112
	December 31, 2012
	Outstanding repurchase agreements	$	13,981,307
	Interest accrued thereon	$	11,717
	Weighted average borrowing rate	0.48		%
	Weighted average remaining maturity (in days)	19.6
	Fair value of the collateral(1)	$	14,693,645
	__________________
	-1	Collateral for repurchase agreements consisted of Agency RMBS and U.S. Treasury Securities.

Share_Capital_Tables

Share Capital (Tables)	9 Months Ended
	Sep. 30, 2013
Stockholders' Equity Note [Abstract]
Common Stock Transactions [Table Text Block]	The Company’s common stock transactions during the nine months ended September 30, 2013 and 2012 are as follows (in thousands):
		Nine Months Ended September 30, 2013					Nine Months Ended September 30, 2012
		Shares		Amount			Shares		Amount
	Shares sold in public offerings or issued as restricted stock	351		$	2,364		92,104		$	1,238,141
	Shares issued in reinvestment of distributions	—		—			98		1,310
	Shares repurchased or canceled	(8,395	)	(72,563		)	(13	)	(180		)
	Net increase (decrease)	(8,044	)	$	(70,199	)	92,189		$	1,239,271

Financial_Highlights_Tables

Financial Highlights (Tables)	9 Months Ended
	Sep. 30, 2013
Financial Highlights [Abstract]
Summary Of Financial Highlight Information	In accordance with financial reporting requirements applicable to investment companies, the Company has included below certain financial highlight information for the three and nine months ended September 30, 2013 and 2012:
		Per Common Share
		Three Months Ended September 30,								Nine Months Ended September 30,
		2013				2012				2013				2012
	Net asset value, beginning of period	$	10.2			$	13.52			$	13.31			$	13.02
	Net income (loss):
	Net investment income	0.4			(a)	0.36			(a)	1.05			(a)	1.32			(a)
	Net gain (loss) from investments and swap and cap contracts	(0.22		)	(a)	1.11			(a)	(3.27		)	(a)	1.88			(a)
	Net income (loss)	0.18				1.47				(2.22		)		3.2
	Dividends on preferred stock	(0.03		)	(a)	(0.01		)	(a)	(0.06		)	(a)	(0.01		)	(a)
	Net income (loss) available to common shares	0.15				1.46				(2.28		)		3.19
	Capital transactions:
	Distributions to common stockholders	(0.34		)		(0.45		)		(1.00		)		(1.45		)
	Issuance/Repurchase of common and preferred shares and amortization of share based compensation	0.09			(a)	(0.07		)	(a)	0.07			(a)	(0.30		)	(a)
	Net decrease in net asset value from capital transactions	(0.25		)		(0.52		)		(0.93		)		(1.75		)
	Net asset value, end of period	$	10.1			$	14.46			$	10.1			$	14.46
	Net asset value total return (%)	2.35		%	(b)	10.28		%	(b)	(16.60		)%	(b)	22.2		%	(b)
	Market value total return (%)	(8.02		)%	(b)	5.59		%	(b)	(23.53		)%	(b)	18.88		%	(b)
	Ratios to Average Net Assets
	Expenses before interest expense	1.13		%	(c)	0.93		%	(c)	1.01		%	(c)	1.16		%	(c)
	Total expenses	3.55		%	(c)	3		%	(c)	3.47		%	(c)	3.21		%	(c)
	Net investment income	13.77		%	(c)	10.33		%	(c)	10.92		%	(c)	12.59		%	(c)
	__________________
	(a)	Calculated based on average shares outstanding during the period. Average shares outstanding include vested and unvested restricted shares and differs from weighted average shares outstanding used in calculating EPS (see Note 3).
	(b)	Not computed on an annualized basis.
	(c)	Computed on an annualized basis.

Organization_Details

Organization (Details) (USD $)	Sep. 30, 2013	Dec. 31, 2012
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Series A Cumulative Redeemable Preferred Stock, liquidation preference per share	$25	$25

Significant_Accounting_Policie2

Significant Accounting Policies (Details) (USD $)	3 Months Ended	9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2013	Dec. 31, 2012
Significant Accounting Policies [Line Items]
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	$19.20	$19.20	$34.10
Collateral Already Posted, Aggregate Fair Value			47.3
Document Period End Date		30-Sep-13
Percentage Of Reit Taxable Income That Must Be Distributed To Stockholders	90.00%
Derivative Asset, Fair Value of Collateral	226.8	226.8
Derivative Asset, Current	267.4	267.4	124.2
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	21.4	21.4	42.8
Agency RMBS [Member]
Significant Accounting Policies [Line Items]
Security Owned and Pledged as Collateral, Fair Value	($5.40)	($5.40)	$10.40
Minimum [Member]
Significant Accounting Policies [Line Items]
Repurchase agreement period (in days)	30
Maximum [Member]
Significant Accounting Policies [Line Items]
Repurchase agreement period (in days)	90

Earnings_Per_Share_Details

Earnings Per Share (Details) (USD $)	3 Months Ended				9 Months Ended
In Thousands, except Share data, unless otherwise specified	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013	Sep. 30, 2012
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Document Period End Date					30-Sep-13
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Number	131,088		131,088		131,088	131,088
Net income	$30,571		$241,907		($383,918)	$412,730
Less preferred stock dividends	-5,203		-953		-10,651	-953
Net income (loss) available to common shares	25,368		240,954		-394,569	411,777
Common shares	-56,444		-78,397		-170,473	-195,175
Unvested shares	-295		-327		-884	-1,083
Undistributed earnings (loss)	($31,371)		$162,230		($565,926)	$215,519
Common shares	169,465,000		164,269,000		172,284,000	128,116,000
Distributed earnings	$0.33		$0.48		$0.99	$1.52
Undistributed earnings (loss)	($0.19)		$0.98		($3.28)	$1.67
Basic earnings (loss) per common share	$0.14		$1.46		($2.29)	$3.19
Net effect of dilutive stock options (1)	0	[1]	0	[1]	0	0
Diluted weighted average shares outstanding	169,465,000		164,269,000		172,284,000	128,116,000
Distributed earnings	$0.33		$0.48		$0.99	$1.52
Undistributed earnings (loss)	($0.19)		$0.98		($3.28)	$1.67
Diluted earnings (loss) per common share	$0.14		$1.46
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Number	131				131
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Exercisable Options, Weighted Average Exercise Price	$30		$30		$30	$30
[1]	For the three and nine months ended SeptemberB 30, 2013 and 2012, the Company had an aggregate of 131 stock options outstanding with a weighted average exercise price of $30.00 that were not included in the calculation of EPS, as their inclusion would have been anti-dilutive. These instruments may have a dilutive impact on future EPS.

Investments_In_Securities_And_2

Investments In Securities And Interest Rate Swap And Cap Contracts (Details) (USD $)	3 Months Ended	12 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
	Y
Schedule of Trading Securities and Other Trading Assets [Line Items]
Maximum Period Of Short Term Assets And Liabilities Are Measured At Deemed To Appropriate Fair Value	1
Unobservable input capitalization minimum rate	4.00%
Percentage of hybrid ARMs reset to variable rate	100.00%
Trading Securities Pledged as Collateral	$92.30	$127.60
Securities Received as Collateral	199.5	18.4
Unobservable input capitalization maximum rate	5.00%
Agency RMBS [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Unamortized premium on marketable securities	$366	$879.60
Debt Instrument, Maturity Date	30
Average final contractual maturity of Agency RMBS portfolio	2036	2033

InvestmentsAssets_And_Liabilit

(Investments)(Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Details) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure	$14,723,661	$20,985,887
Financial Instruments, Owned, at Fair Value	14,456,252	20,861,718	[1]
Derivative Financial Instruments, Liabilities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Liabilities, Fair Value Disclosure	49,537	98,575
US Treasury Bill [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure		37,999
Derivative Financial Instruments, Assets [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure	267,409	124,169
Other Investments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure	6,945	19,576
Agency RMBS [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure	14,449,307	20,804,143
Fair Value, Inputs, Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure	0	37,999
Fair Value, Inputs, Level 1 [Member] | Derivative Financial Instruments, Liabilities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Liabilities, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 1 [Member] | US Treasury Bill [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure		37,999
Fair Value, Inputs, Level 1 [Member] | Derivative Financial Instruments, Assets [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 1 [Member] | Other Investments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 1 [Member] | Agency RMBS [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure	6,945	19,576
Fair Value, Inputs, Level 3 [Member] | Derivative Financial Instruments, Liabilities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Liabilities, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 3 [Member] | US Treasury Bill [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure		0
Fair Value, Inputs, Level 3 [Member] | Derivative Financial Instruments, Assets [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 3 [Member] | Other Investments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure	6,945	19,576
Fair Value, Inputs, Level 3 [Member] | Agency RMBS [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure	14,716,716	20,928,312
Fair Value, Inputs, Level 2 [Member] | Derivative Financial Instruments, Liabilities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Liabilities, Fair Value Disclosure	49,537	98,575
Fair Value, Inputs, Level 2 [Member] | US Treasury Bill [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure		0
Fair Value, Inputs, Level 2 [Member] | Derivative Financial Instruments, Assets [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure	267,409	124,169
Fair Value, Inputs, Level 2 [Member] | Other Investments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 2 [Member] | Agency RMBS [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure	$14,449,307	$20,804,143
[1]	Derived from audited financial statements.

InvestmentsLevel_3_Inputs_Deta

(Investments)(Level 3 Inputs) (Details)	12 Months Ended
	Dec. 31, 2012
Derivative, Fair Value, Net [Abstract]
Weighted Average, Constant Prepayment Rate	20.00%
Weighted Average, Default Rate	2.00%
Weighted Average, Recovery Rate	69.00%
Weighted Average, Recovery Lag	6 Months

InvestmentsSchedule_Of_Fair_Va

(Investments)(Schedule Of Fair Value Reconciliation, Level 3) (Details) (Other Investments [Member], USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Other Investments [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning balance Level 3 assets	$6,945	$24,802	$19,576	$18,675
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales	0	-964	-324	-3,081
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases, Sales, Issuances, Settlements	0	1,483	-6,721	2,799
Change in net unrealized appreciation (depreciation)	0	-8,592	-12,005	-1,664
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings	0	2,648	6,419	2,648
Transfers into (out of) Level 3	0	0	0	0
Ending balance Level 3 assets	$6,945	$19,377	$6,945	$19,377

InvestmentsAgency_RMBS_Portfol

(Investments)(Agency RMBS Portfolio) (Details) (USD $)	1 Months Ended			3 Months Ended								3 Months Ended
	Oct. 31, 2013	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2013		Dec. 31, 2012		Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2013	Dec. 31, 2012	Dec. 31, 2012		Sep. 30, 2013		Dec. 31, 2012		Sep. 30, 2013		Dec. 31, 2012		Sep. 30, 2013		Dec. 31, 2012		Sep. 30, 2013		Dec. 31, 2012
				Agency RMBS [Member]		Agency RMBS [Member]		Agency RMBS [Member]	Agency RMBS [Member]	Agency RMBS [Member]	Agency RMBS [Member]	Agency RMBS [Member]		Agency RMBS [Member]		Agency RMBS [Member]		Agency RMBS [Member]		Agency RMBS [Member]		Agency RMBS [Member]		Agency RMBS [Member]		Agency RMBS [Member]		Agency RMBS [Member]
								Par Value [Member]	Par Value [Member]	Fair Value [Member]	Fair Value [Member]	Ten Year Fixed Rate Residential Mortgage [Member]		Fifteen Year Fixed Rate Residential Mortgage [Member]		Fifteen Year Fixed Rate Residential Mortgage [Member]		20 Year Fixed Rate [Member]		20 Year Fixed Rate [Member]		30 Year Fixed Rate [Member]		30 Year Fixed Rate [Member]		Hybrid ARMs [Member]		Hybrid ARMs [Member]
																										M		M
Investments In Securities And Interest Rate Swap And Cap Contracts [Line Items]
Debt Instrument, Face Amount				$13,987,280,000		$19,681,502,000						$207,091,000		$5,995,535,346		$11,092,374,000		$89,615,315		$1,087,835,000		$5,813,528,918		$3,571,692,000		$2,088,600,621		$3,722,510,000
Assets, Fair Value Disclosure		14,723,661,000	20,985,887,000	14,449,307,000		20,804,143,000						219,747,000		6,240,505,000		11,717,136,000		96,644,000		1,148,932,000		5,985,741,000		3,817,488,000		2,126,417,000		3,900,840,000
Weighted Average, Cost/Par								$102.57	$104.47			$103.60		$102.43		$104.32		$103.08		$104.96		$102.33		$105.78		$103.59		$103.54
Weighted Average, Fair Value/Par										$103.30	$105.70	$106.11		$104.09		$105.63		$107.84		$105.62		$102.96		$106.88		$101.81		$104.79
Weighted Average, MTR																										68.9	[1]	74.3	[1]
Weighted Average, Coupon				3.30%		3.10%						3.50%		3.14%		3.05%		4.50%		3.17%		3.70%		3.59%		2.57%		2.71%
Weighted Average, CPR	5.50%			12.40%	[2]	15.80%	[2]					19.40%	[2]	15.10%	[2]	16.10%	[2]	31.30%	[2]	10.10%	[2]	4.10%	[2]	8.90%	[2]	19.10%	[2]	19.10%	[2]
Percentage of hybrid ARMs reset to variable rate		100.00%
[1]	MTR, or bMonths to Resetb is the weighted average number of months remaining before the fixed rate on a hybrid ARM becomes a variable rate. At the end of the fixed period, the variable rate will be determined by the margin and the pre-specified caps of the ARM. After the fixed period, 100% of the hybrid ARMs in the portfolio reset annually.
[2]	CPR, or bConstant Prepayment Rate,b is a method of expressing the prepayment rate for a mortgage pool that assumes that a constant fraction of the remaining principal is prepaid each month or year. Specifically, the CPR is an annualized version of the prior three month prepayment rate. Securities with no prepayment history are excluded from this calculation.

InvestmentsSummary_Of_Interest

(Investments)(Summary Of Interest Rate Swap And Cap Contracts) (Details) (USD $)	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Summary Of Interest Rate Swap And Cap Contracts [Line Items]
Derivative, Collateral, Obligation to Return Cash	$32,700,000		$28,900,000
DerivativeNotionalTransactions	100,000,000	4,950,000,000
February Two Thousand And Thirteen Opened Type [Member]
Summary Of Interest Rate Swap And Cap Contracts [Line Items]
Trade Date	Feb-13
DerivativeNotionalTransactions	1,500,000,000
April 2012 Opened Type [Member]
Summary Of Interest Rate Swap And Cap Contracts [Line Items]
Trade Date		Apr-12
DerivativeNotionalTransactions		500,000,000
March Two Thousand And Thirteen Terminated Type [Member]
Summary Of Interest Rate Swap And Cap Contracts [Line Items]
Trade Date	Mar-13
DerivativeNotionalTransactions	-500,000,000
May 2012 Opened Type [Member]
Summary Of Interest Rate Swap And Cap Contracts [Line Items]
Trade Date		May-12
DerivativeNotionalTransactions		600,000,000
March Two Thousand And Thirteen Opened Type [Member]
Summary Of Interest Rate Swap And Cap Contracts [Line Items]
Trade Date	Mar-13
DerivativeNotionalTransactions	1,200,000,000
June 2012 Opened Type [Member]
Summary Of Interest Rate Swap And Cap Contracts [Line Items]
Trade Date		Jun-12
DerivativeNotionalTransactions		600,000,000
June Two Thousand And Thirteen Matured Type [Member]
Summary Of Interest Rate Swap And Cap Contracts [Line Items]
Trade Date	Jun-13
DerivativeNotionalTransactions	-300,000,000
August Two Thousand And Thirteen Opened Type [Member]
Summary Of Interest Rate Swap And Cap Contracts [Line Items]
Trade Date	Aug-13
DerivativeNotionalTransactions	500,000,000
August Two Thousand And Thirteen Terminated Type [Member]
Summary Of Interest Rate Swap And Cap Contracts [Line Items]
Trade Date	Aug-13
DerivativeNotionalTransactions	-2,200,000,000
July Two Thousand And Thirteen Matured Type [Member]
Summary Of Interest Rate Swap And Cap Contracts [Line Items]
Trade Date	Jul-13
DerivativeNotionalTransactions	-300,000,000
June Two Thousand And Thirteen Terminated Type [Member]
Summary Of Interest Rate Swap And Cap Contracts [Line Items]
Trade Date	Jun-13
DerivativeNotionalTransactions	-700,000,000
May Two Thousand And Thirteen Matured Type [Member]
Summary Of Interest Rate Swap And Cap Contracts [Line Items]
Trade Date	May-13
DerivativeNotionalTransactions	-100,000,000
May Two Thousand And Thirteen Opened Type [Member]
Summary Of Interest Rate Swap And Cap Contracts [Line Items]
Trade Date	May-13
DerivativeNotionalTransactions	500,000,000
September Two Thousand And Twelve Opened Type [Member]
Summary Of Interest Rate Swap And Cap Contracts [Line Items]
Trade Date		Sep-12
DerivativeNotionalTransactions		1,000,000,000
April Two Thousand And Thirteen Opened Type [Member]
Summary Of Interest Rate Swap And Cap Contracts [Line Items]
Trade Date	Apr-13
DerivativeNotionalTransactions	500,000,000
July Two Thousand And Twelve Opened Type [Member]
Summary Of Interest Rate Swap And Cap Contracts [Line Items]
Trade Date		Jul-12
DerivativeNotionalTransactions		$2,250,000,000

InvestmentsSchedule_Of_Notiona

(Investments)(Schedule Of Notional Amount And Fair Value Of Derivatives) (Details) (Derivatives Not Designated As Hedging Instruments [Member], USD $)	Sep. 30, 2013		Dec. 31, 2012
In Thousands, unless otherwise specified
Interest Rate Swap [Member] | Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount			$1,000,000	[1]
Interest Rate Swap [Member] | Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	3,340,000	[1]	6,490,000	[1]
Interest Rate Derivative Instruments Not Designated as Hedging Instruments, Liability at Fair Value	-49,537	[1]	-98,575	[1]
Interest Rate Swap [Member] | Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	3,750,000	[1]
Interest Rate Derivative Instruments Not Designated as Hedging Instruments, Liability at Fair Value	51,417	[1]	1,180	[1]
Interest Rate Cap Contracts [Member] | Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	3,900,000	[1]	3,400,000	[1]
Interest Rate Cap Contracts [Member] | Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	$215,992	[1]	$122,989	[1]
[1]	See Note 2 for additional information on the Companybs purpose for entering into interest rate swaps and caps and the decision not to designate them as hedging instruments.

Investments_In_Securities_And_3

Investments In Securities And Interest Rate Swap And Cap Contracts (Investments)(Gain or Loss) (Details) (USD $)	3 Months Ended				9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	($53,280)	[1]	($38,618)	[1]	$152,987	[1]	($80,403)	[1]
[1]	See Note 2 for additional information on the Companybs purpose for entering into interest rate swaps and caps and the decision not to designate them as hedging instruments.

Borrowings_Details

Borrowings (Details) (USD $)	Sep. 30, 2013		Dec. 31, 2012
In Thousands, unless otherwise specified	D		D
Short-term Debt [Abstract]
Outstanding repurchase agreements	$11,735,071		$13,981,307	[1]
Interest accrued thereon	2,865		11,717
Weighted average borrowing rate	0.39%		0.48%
Weighted average remaining maturity (in days)	44		19.6
Fair value of the collateral(1)	$12,342,112	[2]	$14,693,645	[2]
Number of repurchase agreements exceeding 10% of net assets	0		0
Schedule of Underlying Assets of Repurchase Agreements when Amount of Repurchase Agreements Exceeds 10 Percent of Assets [Table Text Block]	10.00%		10.00%
RepoPercentageofNetAssets	10.00%
[1]	Derived from audited financial statements.
[2]	Collateral for repurchase agreements consisted of Agency RMBS and U.S. Treasury Securities.

Contingencies_Details

Contingencies (Details) (USD $)	Sep. 30, 2013	Dec. 31, 2012
Commitments and Contingencies Disclosure [Abstract]
Indemnification claims	$0	$0

Share_Capital_Details

Share Capital (Details) (USD $)	9 Months Ended								9 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Apr. 30, 2013	Dec. 31, 2012		Aug. 03, 2012	Jul. 16, 2012	Feb. 01, 2012	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Dec. 31, 2012	Jun. 07, 2011
									Dividend Reinvestment And Direct Stock Purchase Plan [Member]	Dividend Reinvestment And Direct Stock Purchase Plan [Member]	Equity Placement Program [Member]	Equity Placement Program [Member]	Equity Placement Program [Member]	Equity Placement Program [Member]
Equity Issuance [Line Items]
Proceeds from Issuance of Common Stock	($72,772,000)	$1,235,842,000
Common stock, shares authorized	500,000,000			500,000,000
Document Period End Date	30-Sep-13
Stock Repurchased and Retired During Period, Shares	8,400,000
Preferred Stock, Shares Issued	3,000,000			3,000,000		3,000,000
Preferred Stock, Par or Stated Value Per Share	$0.01			$0.01
Series B Cumulative Redeemable Preferred Stock, shares outstanding	8,000,000			0
Series B Cumulative Redeemable Preferred Stock, shares issued	8,000,000		8,000,000	0
Preferred Stock, Dividend Rate, Percentage	7.75%
Stock Repurchased and Retired During Period, Value	-72,563,000	-180,000
Increase (Decrease) In Shares During Period	-8,044,000	92,189,000
Number Of Common Stock Available To Sell Under Sales Agreement												3,081,447	3,081,447	15,000,000
Stock Repurchase Program, Authorized Amount	250,000,000
Public Offering Shares							46,000,000	28,750,000
Common Stock, Shares, Issued	166,880,305			174,924,149
Preferred Stock, Shares Authorized	50,000,000			50,000,000
Net proceeds (payments) from issuance and repurchase of common shares	72,400,000
Shares sold in public offerings or issued as restricted stock, Shares	351,000	92,104,000									11,900,000
Proceeds from Issuance or Sale of Equity	2,364,000	1,238,141,000
Shares sold in public offerings under equity placement program, Amount		164,300,000
Shares issued in reinvestment of distributions, Shares	0	98,000							5,300,000
Treasury Stock Acquired, Average Cost Per Share	$8.62
Increase in net assets from capital transactions	-70,199,000	1,239,271,000
Common stock issued under reinvestment plan, value	0	1,310,000							74,000,000
Stock Repurchased During Period, Shares	-8,395,000	-13,000
Stock Available For Issuance During Period Shares Dividend Reinvestment Plan										4,055,245
Share-based Compensation Arrangement by Share-based Payment Award, Shares Issued in Period	350,807	205,390
Public Offering Price							13.7	13.28
Common Stock, Value, Issued	1,669,000			1,749,000	[1]		622,200,000	377,300,000
us-gaap_PreferredStockDividendRatePercentage_SeriesB	7.50%
Series A Cumulative Redeemable Preferred Stock, liquidation preference per share	$25		$25	$25		$25
Preferred Stock, Value, Issued	72,369,000			72,369,000	[1]	72,400,000
us-gaap_PreferredStockValue_SeriesB	$193,550,000		$193,600,000	$0	[1]
[1]	Derived from audited financial statements.

Financial_Highlights_Details

Financial Highlights (Details) (USD $)	3 Months Ended				9 Months Ended
	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012		Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2012	Dec. 31, 2011
Financial Highlights [Abstract]
Net asset value, end of period	$10.10		$14.46		$10.10		$14.46		$10.20	$13.31	$13.52	$13.02
Net investment income	$0.40	[1]	$0.36	[1]	$1.05	[1]	$1.32	[1]
Net gain (loss) from investments and swap and cap contracts	($0.22)	[1]	$1.11	[1]	($3.27)	[1]	$1.88	[1]
Net income (loss)	$0.18		$1.47		($2.22)		$3.20
Dividends on preferred stock	($0.03)	[1]	($0.01)	[1]	($0.06)	[1]	($0.01)	[1]
Net income (loss) available to common shares	$0.15		$1.46		($2.28)		$3.19
Distributions to common stockholders	($0.34)		($0.45)		($1)		($1.45)
Issuance/Repurchase of common and preferred shares and amortization of share based compensation	$0.09	[1]	($0.07)	[1]	$0.07	[1]	($0.30)	[1]
Net decrease in net asset value from capital transactions	($0.25)		($0.52)		($0.93)		($1.75)
Net asset value total return (%)	2.35%	[2]	10.28%	[2]	-16.60%	[2]	22.20%	[2]
Market value total return (%)	-8.02%	[2]	5.59%	[2]	-23.53%	[2]	18.88%	[2]
Expenses before interest expense	1.13%	[3]	0.93%	[3]	1.01%	[3]	1.16%	[3]
Total expenses	3.55%	[3]	3.00%	[3]	3.47%	[3]	3.21%	[3]
Net investment income	13.77%	[3]	10.33%	[3]	10.92%	[3]	12.59%	[3]
[1]	Calculated based on average shares outstanding during the period. Average shares outstanding include vested and unvested restricted shares and differs from weighted average shares outstanding used in calculating EPS (see Note 3).
[2]	Not computed on an annualized basis.
[3]	Computed on an annualized basis.

Subsequent_Events_Details

Subsequent Events (Details)	1 Months Ended
	Oct. 31, 2013
Subsequent Event [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period	13,937
Weighted Average, CPR	5.50%