Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Principal amount of loans payable	$ 145.3	$ 144.4
Common stock, units issued (in shares)	91,051,380	84,610,951
Common stock, units outstanding (in shares)	91,051,380	84,610,951