CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY
Change in the fair value of interest rate swap contracts, income tax effect (in dollars)		$ 1,574	$ 3,471
Pension and other post-retirement liabilities, income tax effect (in dollars)	$ 7,807	$ 7,239	$ 2,056
Exercise of stock options, shares	93,839	878,658	790,596
Shares issued under stock incentive plan	315,030	762,004	50,446
Shares issued under employee stock purchase plan		2,567	3,251
Shares issued to Board of Directors in lieu of cash	3,391	2,739	3,603
Cash dividend (in dollars per share)	$ 0.44	$ 0.36	$ 0.12
Purchase of common stock, shares	310,252	768,780	869,065