Consolidated Statements of Income (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Interest income:
Mortgage-backed securities	$ 354,436	$ 450,708	$ 504,800
Mortgage loans held for investment	35
Short-term cash investments	1,283	1,560	1,508
Total interest income	355,754	452,268	506,308
Interest expense	132,495	197,709	197,064
Net interest margin	223,259	254,559	309,244
Operating expenses:
Management fee	16,532	18,180	17,420
Share-based compensation	3,612	2,594	1,920
General and administrative	10,525	7,092	5,006
Total operating expenses	30,669	27,866	24,346
Other income (loss):
Net realized gain (loss) on sale of mortgage-backed securities	5,196	(283,012)	64,347
Impairment of mortgage-backed securities		(8,102)
Gain on mortgage loans held for investment	8
Loss on derivative instruments, net	(141,433)	(69,715)
Total other income (loss)	(136,229)	(360,829)	64,347
Net income (loss)	56,361	(134,136)	349,245
Dividends on preferred stock	21,922	21,922	7,551
Net income (loss) available to common shareholders	$ 34,439	$ (156,058)	$ 341,694
Earnings (loss) per share - common stock, basic	$ 0.36	$ (1.59)	$ 3.67
Earnings (loss) per share - common stock, diluted	$ 0.36	$ (1.59)	$ 3.67
Dividends per share of common stock	$ 2.00	$ 2.45	$ 3.30
Weighted average common shares outstanding, basic	96,603,634	98,337,362	93,185,520
Weighted average common shares outstanding, diluted	96,603,634	98,337,362	93,185,520