Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Statement of Financial Position [Abstract]
Securities held to maturity, fair value	$ 444,926	$ 408,576
Preferred stock, par value (usd per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized (shares)	5,000,000	5,000,000
Preferred stock, shares issued (shares)	0	0
Preferred stock, shares outstanding (shares)	0	0
Common stock, par value (usd per share)	$ 5.00	$ 5.00
Common stock, shares authorized (shares)	75,000,000	75,000,000
Common stock, shares issued (shares)	32,656,166	32,656,182
Common stock, shares outstanding (shares)	31,533,703	31,387,668