CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY (Parenthetical) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Issuance of stock to employees under benefit plans, shares withheld for payroll tax	$ 11,582	$ 12,297	$ 7,269
Unrealized gain on marketable securities, tax portion	169	666	0
Amortization of prior service costs, tax	$ (134)	$ 9	$ 0