CONSOLIDATED STATEMENT OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Preferred Stock [Member]	Common Stock [Member]	Additional Paid In Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income [Member]
Total stockholders' equity		$ 36,104	$ 21,724	$ 939,674	$ 1,087,617	$ (40,415)
Balance at beginning of period at Dec. 31, 2018		36,104	21,724	939,674	1,087,617	(40,415)
Common stock withheld for taxes			(18)	(1,941)
Restricted stock grants			31	(31)
Unrestricted stock grants			0	0
Stock-based compensation				2,997
Net income	$ 130,928				130,928
Dividends on common stock					(19,607)
Dividends on preferred stock					(2,007)
Other comprehensive income, net of tax	45,539					45,539
Balance at end of period at Sep. 30, 2019	2,200,595	36,104	21,736	940,700	1,196,931	5,124
Total stockholders' equity	2,200,595	36,104	21,736	940,700	1,196,931	5,124
Total stockholders' equity		36,104	21,733	939,769	1,157,808	(2,438)
Balance at beginning of period at Jun. 30, 2019		36,104	21,733	939,769	1,157,808	(2,438)
Common stock withheld for taxes			(1)	(53)
Restricted stock grants			5	(5)
Unrestricted stock grants			0	0
Stock-based compensation				988
Net income	46,327				46,327
Dividends on common stock					(6,535)
Dividends on preferred stock					(669)
Other comprehensive income, net of tax	7,562					7,562
Balance at end of period at Sep. 30, 2019	2,200,595	36,104	21,736	940,700	1,196,931	5,124
Total stockholders' equity	2,200,595	36,104	21,736	940,700	1,196,931	5,124
Total stockholders' equity	2,200,595	36,104	21,736	940,700	1,196,931	5,124
Total stockholders' equity	2,228,073	36,104	21,736	941,652	1,221,817	6,764
Balance at beginning of period at Dec. 31, 2019	2,228,073	36,104	21,736	941,652	1,221,817	6,764
Common stock withheld for taxes			(5)	(201)
Restricted stock grants			90	(90)
Unrestricted stock grants			2	(2)
Stock-based compensation				3,854
Net income	52,135				52,135
Dividends on common stock					(32,808)
Dividends on preferred stock					(2,007)
Other comprehensive income, net of tax	38,563					38,563
Balance at end of period at Sep. 30, 2020	2,225,282	36,104	21,823	945,213	1,176,815	45,327
Total stockholders' equity	2,228,073	36,104	21,823	945,213	1,176,815	45,327
Total stockholders' equity		36,104	21,816	943,816	1,159,828	53,270
Balance at beginning of period at Jun. 30, 2020		36,104	21,816	943,816	1,159,828	53,270
Common stock withheld for taxes			0	(8)
Restricted stock grants			5	(5)
Unrestricted stock grants			2	(2)
Stock-based compensation				1,412
Net income	28,613				28,613
Dividends on common stock					(10,957)
Dividends on preferred stock					(669)
Other comprehensive income, net of tax	(7,943)					(7,943)
Balance at end of period at Sep. 30, 2020	2,225,282	36,104	21,823	945,213	1,176,815	45,327
Total stockholders' equity	2,225,282	36,104	21,823	945,213	1,176,815	45,327
Total stockholders' equity	$ 2,225,282	$ 36,104	$ 21,823	$ 945,213	$ 1,176,815	$ 45,327