Subsequent Events - Additional Information (Details) - USD ($)											3 Months Ended		6 Months Ended
	Apr. 27, 2016	Apr. 06, 2016	Mar. 28, 2016	Mar. 27, 2016	Mar. 13, 2016	Feb. 27, 2016	Feb. 26, 2016	Feb. 13, 2016	Jan. 27, 2016	Jan. 15, 2016	Mar. 31, 2016	Mar. 31, 2015	Jun. 30, 2016
Subsequent Event [Line Items]
Common stock dividends cash paid (in dollars per share)				$ 0.33		$ 0.33			$ 0.33
Aggregate amount paid to holders of record (in dollars)				$ 12,131,000		$ 12,131,000			$ 12,131,000		$ 36,393,000	$ 42,486,000
Common stock dividends declared per common share (in dollars per share)					$ 0.33			$ 0.33		$ 0.33	$ 0.99	$ 0.96
Series A Preferred Stock
Subsequent Event [Line Items]
Preferred stock dividends cash paid (in dollars per share)			$ 0.171875				$ 0.171875		$ 0.171875
Aggregate amount paid to holders of record (in dollars)			$ 374,800				$ 374,800		$ 374,800		$ 1,124,400	$ 1,124,000
Series B Preferred Stock
Subsequent Event [Line Items]
Preferred stock dividends cash paid (in dollars per share)			$ 0.1640625				$ 0.1640625		$ 0.1640625
Aggregate amount paid to holders of record (in dollars)			$ 927,000				$ 927,000		$ 927,000		$ 2,781,000	$ 2,781,000
Javelin Mortgage Investment Corp. | Scenario, Forecast | Other Income
Subsequent Event [Line Items]
Bargain purchase price, gain													$ 6,500,000
Subsequent Event
Subsequent Event [Line Items]
Common stock dividends cash paid (in dollars per share)	$ 0.27
Aggregate amount paid to holders of record (in dollars)	$ 9,907,000
Common stock dividends declared per common share (in dollars per share)	$ 0.22
Subsequent Event | Series A Preferred Stock
Subsequent Event [Line Items]
Preferred stock dividends cash paid (in dollars per share)	$ 0.17
Aggregate amount paid to holders of record (in dollars)	$ 375,000
Rate per preferred share dividends declared (in dollars per share)	$ 0.17
Subsequent Event | Series B Preferred Stock
Subsequent Event [Line Items]
Preferred stock dividends cash paid (in dollars per share)	$ 0.16
Aggregate amount paid to holders of record (in dollars)	$ 927,000
Rate per preferred share dividends declared (in dollars per share)	$ 0.16
Subsequent Event | Javelin Mortgage Investment Corp.
Subsequent Event [Line Items]
Payments to acquire businesses, gross		$ 85,200,000
Subsequent Event | Management Agreement | ACM
Subsequent Event [Line Items]
Due from (to) related party		$ 3,400,000