Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Statement Of Income And Comprehensive Income [Abstract]
Net income (loss)	$ 51,620	$ 56,361	$ (134,136)
Other comprehensive income (loss):
Net unrealized gains (losses) on securities available for sale	(133,867)	122,824	(391,590)
Net unrealized gains on derivative instruments	26,760	90,993	120,684
Other comprehensive income (loss)	(107,107)	213,817	(270,906)
Comprehensive income (loss)	(55,487)	270,178	(405,042)
Dividends on preferred stock	21,922	21,922	21,922
Comprehensive income (loss) available to common shareholders	$ (77,409)	$ 248,256	$ (426,964)