CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($)	9 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
MSR Related Assets, pledged as collateral (in dollars)	$ 565,272,000	$ 482,158,000
Residential whole loans, carrying value	1,149,293,000	448,689,000
Residential whole loans, fair value	$ 685,095,000	$ 996,226,000
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized	8,050,000	8,050,000
Preferred stock, dividend rate (as a percent)	7.50%	7.50%
Preferred stock, shares issued	8,000,000	8,000,000
Preferred stock, shares outstanding	8,000,000	8,000,000
Preferred stock, aggregate liquidation preference (in dollars)	$ 200,000,000	$ 200,000,000
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized	886,950,000	886,950,000
Common stock, shares issued	449,472,000	397,831,000
Common stock, shares outstanding	449,472,000	397,831,000
Collateral Pledged | Agency MBS
Securities, at fair value, pledged as collateral	$ 2,795,273,000	$ 2,727,510,000
Collateral Pledged | Non-Agency MBS
Securities, at fair value, pledged as collateral	3,237,108,000	2,379,523,000
Collateral Pledged | CRT securities
Securities, at fair value, pledged as collateral	$ 504,931,000	$ 595,900,000