Consolidated Statements of Changes in Shareholders' Equity (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
Unrealized holding (losses) gains arising during period, taxes	$ 8,266	$ 2,651
Realized net gains	2,665	1,119
Unrealized losses on securities transferred to held-to-maturity, taxes	9,206
Pension liability adjustment, taxes	$ 346	$ 324
Conversion of class B common stock to class A common stock, shares	8,700	7,500
Stock options exercised, shares	1,625	5,987
Class A Common Stock [Member]
Cash dividends paid, per share	$ 0.36	$ 0.36
Class B Common Stock [Member]
Cash dividends paid, per share	$ 0.18	$ 0.18