Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical) - USD ($) $ in Thousands |
Jun. 30, 2016 |
Dec. 31, 2015 |
|---|---|---|
| Statement Of Financial Position [Abstract] | ||
| Pledged securities included in debt securities | $ 117,647 | $ 122,441 |
| Preferred stock, par value | $ 0.00001 | $ 0.00001 |
| Preferred stock, shares authorized | 500,000 | 500,000 |
| Preferred stock, outstanding | 0 | 0 |
| Common stock, par value | $ 0.00001 | $ 0.00001 |
| Common stock, shares authorized | 300,000,000 | 300,000,000 |
| Common stock, shares outstanding | 109,699,000 | 109,098,000 |