Accrued Liabilities (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008
Accrued Liabilities - (Details) [Abstract]
Wages and other compensation	$ 105,955	$ 91,181
Commissions	12,132	12,086
Warranty	8,147	7,038	7,341	9,885
Accrued dividend	13,297	10,456
Deferred revenue	94,761	93,498
Billings in excess of cost	6,351	6,763
Customer deposits	20,095	13,941
Interest	26,744	26,404
Other	35,422	36,713
Accrued Liabilities	$ 322,904	$ 298,080