Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Consolidated Balance Sheets [Abstract]
Securities available for sale, amortized cost	$ 2,562,000	$ 2,086,745
Securities held to maturity, fair value	2,470,117	2,375,851
Property and equipment, accumulated depreciation	$ 231,127	$ 209,763
Common stock, par value per share	$ 3.33	$ 3.33