Consolidated Statements of Shareholders' Equity (Parenthetical) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Consolidated Statements of Shareholders' Equity and Comprehensive Income [Abstract]
Change in fair value of available-for-sale securities, tax effect	$ 1,002	$ 16,766	$ (3,219)
Change in pension funding status, tax effect	$ (4,946)	$ (9,166)	$ (544)
Cash dividends declared (in dollars per share)	$ 0.04	$ 0.14	$ 0.88