Consolidated Statements Of Income (USD $)	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Interest income:
Residential mortgage investments	$ 65,733,000	$ 53,141,000
Other	150,000	113,000
Interest income	65,883,000	53,254,000
Interest expense:
Repurchase arrangements and similar borrowings	(14,103,000)	(12,322,000)
Unsecured borrowings	(2,187,000)	(2,187,000)
Other		(4,000)
Interest expense	(16,290,000)	(14,513,000)
Net interest income (expense)	49,593,000	38,741,000
Other revenue (expense):
Miscellaneous other revenue (expense)	(169,000)	(218,000)
Incentive compensation	(1,538,000)	(1,233,000)
Salaries and benefits	(1,827,000)	(1,700,000)
Other general and administrative expense	(954,000)	(963,000)
Operating expenses	(4,488,000)	(4,114,000)
Income before equity in earnings of unconsolidated affiliates	45,105,000	34,627,000
Equity in earnings of unconsolidated affiliates	65,000	65,000
Net income	45,170,000	34,692,000
Net income available to common stockholders:
Net income	45,170,000	34,692,000
Less cash dividends paid on preferred shares	(5,213,000)	(5,058,000)
Net income (loss) available to common stockholders, basic, total	$ 39,957,000	$ 29,634,000
Net income per common share:
Basic	$ 0.45	$ 0.41
Diluted	$ 0.44	$ 0.41
Cash dividends declared per share:
Common	$ 0.430	$ 0.410
$1.60 Cumulative Preferred Stock, Series A [Member]
Cash dividends declared per share:
Preferred	$ 0.400	$ 0.400
$1.26 Cumulative Convertible Preferred Stock, Series B [Member]
Cash dividends declared per share:
Preferred	$ 0.315	$ 0.315