CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY (unaudited) - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Balances at beginning at Dec. 31, 2018	$ 1,971,344	$ 957	$ 1,699,031	$ 293,777	$ (22,421)
Balances at beginning, shares at Dec. 31, 2018		95,679,596
Net income	44,643			44,643
Unrealized holding gain (loss) on available for sale securities, net of deferred income tax	21,558				21,558
Cumulative adjustment pursuant to adoption of ASU | Accounting Standards Update 2016-02 [Member]	(1,464)			(1,464)
Dividends paid - common	(10,547)			(10,547)
Stock grants issued		$ 1	(1)
Stock grants issued, shares		132,918
Stock based compensation expense	1,218		1,218
Stock options exercised	1,199	$ 1	1,198
Stock options exercised, shares		116,764
Stock repurchase	(399)		(399)
Stock repurchase, shares		(15,971)
Balances at ending at Mar. 31, 2019	2,027,552	$ 959	1,701,047	326,409	(863)
Balances at ending, shares at Mar. 31, 2019		95,913,307
Balances at beginning at Dec. 31, 2019	$ 2,896,718	$ 1,252	2,407,385	465,680	22,401
Balances at beginning, shares at Dec. 31, 2019	125,173,597	125,173,597
Net income	$ 35,432			35,432
Unrealized holding gain (loss) on available for sale securities, net of deferred income tax	39,729				39,729
Unrealized holding loss on interest rate swaps, net of deferred income tax	(5,740)				(5,740)
Cumulative adjustment pursuant to adoption of ASU	1,093
Cumulative adjustment pursuant to adoption of ASU | Accounting Standards Update 2016-13 [Member]	(47,751)			(47,751)
Dividends paid - common	(17,377)			(17,377)
Stock grants issued		$ 3	(3)
Stock grants issued, shares		258,616
Stock based compensation expense	1,796		1,796
Stock options exercised	1,359	$ 1	1,358
Stock options exercised, shares		179,174
Stock repurchase	(33,914)	$ (15)	(33,899)
Stock repurchase, shares		(1,479,986)
Balances at ending at Mar. 31, 2020	$ 2,870,252	$ 1,241	$ 2,376,637	$ 435,984	$ 56,390
Balances at ending, shares at Mar. 31, 2020	124,131,401	124,131,401