CONSOLIDATED BALANCE SHEETS (Unaudited) (Parenthetical) - USD ($)	Sep. 30, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Securities held-to-maturity, fair value	$ 192,500,000	$ 20,830,000
Preferred stock, par value (in dollars per share)	$ 0	$ 0
Preferred stock, shares authorized (in shares)	10,000,000	10,000,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 1	$ 1
Common stock, shares authorized (in shares)	180,000,000	90,000,000
Common stock, shares issued (in shares)	77,867,000	77,740,000
Common stock, shares outstanding (in shares)	77,867,000	77,740,000