Consolidated Statements of Shareholders' Equity (Parenthetical) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Issuance of stock to employees under benefit plans, shares withheld for payroll tax	$ 12,192	$ 11,582	$ 12,297
Unrealized gain on marketable securities, tax portion	216	370	1,247
Reclassification adjustment for gains included in net income, tax	(257)	(201)	(581)
Amortization of prior service costs, tax	$ (159)	$ (134)	$ 9