CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Investments under fair value option	$ 14,323	$ 160,851
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized (in shares)	50,000,000.0	50,000,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Class A
Common stock, shares authorized (in shares)	950,000,000.0	905,000,000
Common stock, shares issued (in shares)	128,538,703	83,410,376
Common stock, shares outstanding (in shares)	128,538,703	83,410,376
Class B-3
Common stock, shares authorized (in shares)	0	45,000,000
Common stock, shares issued (in shares)	0	44,399,444
Common stock, shares outstanding (in shares)	0	44,399,444