Consolidated Statements of Stockholders' Equity (Parenthetical) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Stock option exercises, tax benefit	$ 580	$ 2,576	$ 2,952
Net issuance of treasury stock for vested restricted stock units, tax benefit	$ 721	$ 1,856	$ 408
Treasury shares netted from common stock shares issued for two-for-one stock split			5,171