Repurchase Agreements (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013
REPURCHASE AGREEMENTS [Abstract]
Repurchase Agreements, Maturities	P93D	P114D
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Repurchase agreement, balance	$ 3,485,544		$ 3,580,754
Repurchage agreement, Weighted Average Interest Rate	0.59%		0.61%
Pledged Financial Instruments, Not Separately Reported, Mortgage-Related Securities Available-for-sale or Held-for-investment	3,814,355		3,890,066
Deferred Costs	(139)		(243)
Bonds [Member]
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Repurchase agreement, balance	16,692		20,651
Repurchage agreement, Weighted Average Interest Rate	1.52%		1.59%
Pledged Financial Instruments, Not Separately Reported, Mortgage-Related Securities Available-for-sale or Held-for-investment	18,607		19,686
Residential Mortgage Backed Securities [Member] | Agency MBS [Member]
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Repurchase agreement, balance	2,350,781		2,522,503
Repurchage agreement, Weighted Average Interest Rate	0.39%		0.42%
Pledged Financial Instruments, Not Separately Reported, Mortgage-Related Securities Available-for-sale or Held-for-investment	2,421,202		2,598,158
Residential Mortgage Backed Securities [Member] | Non-Agency MBS [Member]
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Repurchase agreement, balance	11,905		10,569
Repurchage agreement, Weighted Average Interest Rate	1.77%		1.80%
Pledged Financial Instruments, Not Separately Reported, Mortgage-Related Securities Available-for-sale or Held-for-investment	14,691		12,746
Commercial Mortgage Backed Securities [Member] | Agency MBS [Member]
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Repurchase agreement, balance	265,475		246,849
Repurchage agreement, Weighted Average Interest Rate	0.37%		0.39%
Pledged Financial Instruments, Not Separately Reported, Mortgage-Related Securities Available-for-sale or Held-for-investment	330,182		306,318
Commercial Mortgage Backed Securities [Member] | Non-Agency MBS [Member]
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Repurchase agreement, balance	309,398		303,674
Repurchage agreement, Weighted Average Interest Rate	1.22%		1.27%
Pledged Financial Instruments, Not Separately Reported, Mortgage-Related Securities Available-for-sale or Held-for-investment	371,273		367,859
CMBS IO [Member] | Agency MBS [Member]
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Repurchase agreement, balance	382,327		369,948
Repurchage agreement, Weighted Average Interest Rate	1.14%		1.16%
Pledged Financial Instruments, Not Separately Reported, Mortgage-Related Securities Available-for-sale or Held-for-investment	471,173		449,072
CMBS IO [Member] | Non-Agency MBS [Member]
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Repurchase agreement, balance	149,105		106,803
Repurchage agreement, Weighted Average Interest Rate	1.23%		1.27%
Pledged Financial Instruments, Not Separately Reported, Mortgage-Related Securities Available-for-sale or Held-for-investment	$ 187,227		$ 136,227