Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	Total	Preferred Stock	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Retained Earnings
Stockholders' equity at beginning of period at Dec. 31, 2018	$ 2,399,101	$ 0	$ 90,369	$ 811,186	$ (52,432)	$ 1,549,978
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(30,010)					(30,010)
Other comprehensive income (loss)	566,129				566,129
Share-based compensation	4,205			4,205
Issuance of common stock under compensation plans	112		415	(303)
Stockholders' equity at end of period at Mar. 31, 2019	2,939,537	0	90,784	815,088	513,697	1,519,968
Stockholders' equity at beginning of period at Dec. 31, 2019	4,570,119	16	91,107	1,212,311	1,497,921	1,768,764
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	242,947					242,947
Other comprehensive income (loss)	(1,277,947)				(1,277,947)
Share-based compensation	2,289			2,289
Issuance of common stock under compensation plans	1,255		391	864
Cumulative effect of change in accounting principal	(9,295)					(9,295)
Dividends on preferred stock	(6,611)					(6,611)
Stockholders' equity at end of period at Mar. 31, 2020	$ 3,522,757	$ 16	$ 91,498	$ 1,215,464	$ 219,974	$ 1,995,805