Overview and Summary of Accounting Policies - Narrative (Details) (USD $) In Thousands, unless otherwise specified										9 Months Ended
	Sep. 30, 2014	Jun. 30, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Dec. 31, 2012	Sep. 30, 2014 Prior to December 31, 2013	Sep. 30, 2014 Subsequent to December 31, 2013	Sep. 30, 2014 Subsequent to December 31, 2013 Warranty obligations, fair value option	Sep. 30, 2014 Maximum
Accounting Policies [Line Items]
Product warranty term										25 years
Warranty obligation	$ 32,307	$ 32,969	$ 30,432	$ 29,366	$ 26,777	$ 21,338	$ 29,200	$ 3,100	$ 3,000