CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement of Stockholders' Equity [Abstract]
Issuance of common stock for dividend reinvestment plan (in shares)	42,872	43,650	44,575
Net issuance of common stock (in shares)			2,185,000
Dividends paid on common stock (in dollars per share)	$ 1.20	$ 1.11	$ 1.01
Purchase of common stock (in shares)	1,459,148	0	443,426
Net issuance of common stock under employee stock plan (in shares)	140,692	159,356	108,225
Common Stock Dividends (in shares)		719,515	1,252,353
Net issuance of common stock in connection with the acquisition of Diboll State Bancshares, Inc. (in shares)		5,534,925