Condensed Consolidated Statements of Changes in Shareholders' Equity - USD ($) $ in Thousands	Common Stock	Surplus	Retained Earnings Cumulative Effect of Adoption of ASU	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Cumulative Effect of Adoption of ASU	Total
Balance at Dec. 31, 2019	$ 84,361	$ 1,607,740		$ 679,895	$ 1,017		$ 2,373,013
Balance (in shares) at Dec. 31, 2019	33,744,385
Increase (Decrease) in Stockholders' Equity
Net income				34,396			34,396
Other comprehensive Income (loss), net of tax effects					16,029		16,029
Total comprehensive income							50,425
Cash dividends declared on common stock per share				(64,907)			(64,907)
Employee stock purchases	$ 40	767					807
Employee stock purchases (in shares)	16,217
Stock options exercised	$ 58	682					740
Stock options exercised (in shares)	23,012
Restricted stock awards (forfeitures)	$ 22	(22)
Restricted stock awards (forfeitures) (in shares)	8,828
Stock issued pursuant to restricted stock units	$ 766	(766)
Stock issued pursuant to restricted stock units (in shares)	306,282
Common stock repurchased - buyback plan	$ (800)	(23,915)					(24,715)
Common stock repurchased - buyback plan (in shares)	(320,000)
Common stock repurchased	$ (304)	(7,334)					(7,638)
Common stock repurchased (in shares)	(121,489)
Share-based compensation expense		18,694					18,694
Common stock issued for acquisition	$ 93,178	2,153,149					2,246,327
Common stock issued for acquisition (in shares)	37,271,069
Stock options and restricted stock acquired and converted pursuant to CenterState acquisition		15,487					15,487
Balance (ASU 2016-13) at Sep. 30, 2020			$ (44,820)			$ (44,820)
Balance at Sep. 30, 2020	$ 177,321	3,764,482		604,564	17,046		4,563,413
Balance (in shares) at Sep. 30, 2020	70,928,304
Balance at Jun. 30, 2020	$ 177,268	3,759,166		542,677	12,739		4,491,850
Balance (in shares) at Jun. 30, 2020	70,907,119
Increase (Decrease) in Stockholders' Equity
Net income				95,221			95,221
Other comprehensive Income (loss), net of tax effects					4,307		4,307
Total comprehensive income							99,528
Cash dividends declared on common stock per share				(33,334)			(33,334)
Employee stock purchases	$ 23	399					422
Employee stock purchases (in shares)	9,316
Stock options exercised	$ 14	166					180
Stock options exercised (in shares)	5,471
Stock issued pursuant to restricted stock units	$ 26	(26)
Stock issued pursuant to restricted stock units (in shares)	10,207
Common stock repurchased	$ (10)	(183)					(193)
Common stock repurchased (in shares)	(3,809)
Share-based compensation expense		4,960					4,960
Balance (ASU 2016-13) at Sep. 30, 2020			$ (44,820)			$ (44,820)
Balance at Sep. 30, 2020	$ 177,321	3,764,482		604,564	17,046		4,563,413
Balance (in shares) at Sep. 30, 2020	70,928,304
Balance at Dec. 31, 2020	$ 177,434	3,765,406		657,451	47,589		$ 4,647,880
Balance (in shares) at Dec. 31, 2020	70,973,477						70,973,477
Increase (Decrease) in Stockholders' Equity
Net income				368,697			$ 368,697
Other comprehensive Income (loss), net of tax effects					(48,109)		(48,109)
Total comprehensive income							320,588
Cash dividends declared on common stock per share				(100,990)			(100,990)
Cash dividends equivalents paid on restricted stock units				(114)			(114)
Employee stock purchases	$ 40	1,111					1,151
Employee stock purchases (in shares)	15,920
Stock options exercised	$ 129	2,251					2,380
Stock options exercised (in shares)	51,620
Stock issued pursuant to restricted stock units	$ 187	(187)
Stock issued pursuant to restricted stock units (in shares)	74,878
Common stock repurchased - buyback plan	$ (2,964)	(93,216)					(96,180)
Common stock repurchased - buyback plan (in shares)	(1,185,491)
Common stock repurchased	$ (31)	(938)					(969)
Common stock repurchased (in shares)	(12,367)
Share-based compensation expense		19,195					19,195
Balance at Sep. 30, 2021	$ 174,795	3,693,622		925,044	(520)		$ 4,792,941
Balance (in shares) at Sep. 30, 2021	69,918,037						69,918,037
Balance at Jun. 30, 2021	$ 175,957	3,720,946		836,584	24,136		$ 4,757,623
Balance (in shares) at Jun. 30, 2021	70,382,728
Increase (Decrease) in Stockholders' Equity
Net income				122,788			122,788
Other comprehensive Income (loss), net of tax effects					(24,656)		(24,656)
Total comprehensive income							98,132
Cash dividends declared on common stock per share				(34,305)			(34,305)
Cash dividends equivalents paid on restricted stock units				(23)			(23)
Employee stock purchases	$ 22	645					667
Employee stock purchases (in shares)	8,823
Stock options exercised	$ 22	451					473
Stock options exercised (in shares)	8,923
Stock issued pursuant to restricted stock units	$ 8	(8)
Stock issued pursuant to restricted stock units (in shares)	3,108
Common stock repurchased - buyback plan	$ (1,214)	(34,805)					(36,019)
Common stock repurchased - buyback plan (in shares)	(485,491)
Common stock repurchased		(3)					(3)
Common stock repurchased (in shares)	(54)
Share-based compensation expense		6,396					6,396
Balance at Sep. 30, 2021	$ 174,795	$ 3,693,622		$ 925,044	$ (520)		$ 4,792,941
Balance (in shares) at Sep. 30, 2021	69,918,037						69,918,037