Product Warranties (Provision for warranty obligations) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Product Warranties Disclosures [Abstract]
Product warranty period, maximum	50 years
Product Warranty Accrual [Roll Forward]
Balance at beginning of period	$ 35,818	$ 32,930	$ 30,144
Acquisitions	0	3,389	0
Warranty claims paid during the period	(51,941)	(52,011)	(55,314)
Pre-existing warranty accrual adjustment during the period	0	0	0
Warranty expense during the period	45,473	51,510	58,100
Balance at end of period	$ 29,350	$ 35,818	$ 32,930