Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Statement Of Financial Position [Abstract]
Fair value of held-to-maturity investment securities	$ 57,499	$ 66,853
Accumulated amortization and fair value adjustments on other intangibles	$ 11,674	$ 10,300
Common stock, par value	$ 5	$ 5
Common stock, shares authorized	48,000,000	48,000,000
Common stock, shares issued	18,266,404	18,266,404
Common stock, shares outstanding	16,248,495	16,287,812
Treasury stock, shares	2,017,909	1,978,592