Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Investment securities - held-to-maturity, fair value	$ 0	$ 506,103
Common stock, stated value	$ 1.00	$ 1.00
Authorized and unissued common shares reserved for issuance	300,000,000	300,000,000
Common stock, shares issued	169,616,000	175,141,000
Common stock, shares outstanding	169,616,000	175,141,000
Series A Preferred Stock [Member]
Preferred stock, shares authorized	2,000,000	2,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0