Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014
Assets
Related party accounts receivable	$ 17.8	$ 18.0
Related party loan purchases and originations	39.0	0.0
Fair value of unconsolidated investments	$ 206.1	$ 85.9
Stockholders' Equity Attributable to Parent [Abstract]
Common stock, shares issued (in shares)	112,883,333	96,091,446
Common stock, shares outstanding (in shares)	112,883,333	96,091,446
Cumulative Preferred Stock Subject to Mandatory Redemption [Member]
Stockholders' Equity Attributable to Parent [Abstract]
Preferred stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Preferred stock, shares authorized (in shares)	1,000,000	1,000,000
Cumulative preferred stock, liquidation preference (in dollars per share)	$ 1,000	$ 1,000
Mortgages [Member]
Liabilities
Mortgage investment debt	$ 2,849.7	$ 2,195.9