Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
FHLB advances	$ 657,000	$ 670,000
Class A Common Stock
Common stock, par value (usd per share)	$ 0.001	$ 0.001
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares issued	49,348,492	47,065,593
Common stock, shares outstanding	46,620,627	44,371,104
Treasury stock, shares	2,727,865	2,694,489
Class B Non-voting Common Stock
Common stock, par value (usd per share)	$ 0.001	$ 0.001
Common stock, shares authorized	50,000,000	50,000,000
Common stock, shares issued	192,132	192,132
Common stock, shares outstanding	0	0
Treasury stock, shares	192,132	192,132