Condensed consolidated statements of comprehensive income (loss) (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 1,207	$ 15,905	$ 31,581	$ 38,665
Other comprehensive income, net of tax:
Net change in unrealized gain in available-for-sale securities, net of tax of $38 and $187 and $802 and $298	(1,524)	3,868	10,246	4,584
Reclassification adjustment for gain on sale of securities included in net income, net of tax expense of $57 and $3 and $298 and $101	(359)	(44)	(4,109)	(1,741)
Comprehensive income (loss)	$ (676)	$ 19,729	$ 37,718	$ 41,508