Segment Reporting, Sales to Major Customers (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Schedule Of Revenue By Major Customers By Reporting Segments [Abstract]
Number of major customers	3
Minimum percentage of sales for major customer (in hundredths)	10.00%
Sales by customers [Member]
Revenue, Major Customer [Line Items]
Amount	$ 266,955,000	$ 242,259,000	$ 290,209,000
% of Sales (in hundredths)	37.80%	37.70%	36.50%
Sales by product grouping [Member]
Revenue, Major Customer [Line Items]
% of Sales (in hundredths)	100.00%	100.00%	100.00%
Customer One [Member] | Sales by customers [Member]
Revenue, Major Customer [Line Items]
Amount	99,382,000	91,886,000	123,459,000
% of Sales (in hundredths)	14.10%	14.30%	15.50%
Customer Two [Member] | Sales by customers [Member]
Revenue, Major Customer [Line Items]
Amount	93,298,000	90,624,000	101,895,000
% of Sales (in hundredths)	13.20%	14.10%	12.80%
Customer Three [Member] | Sales by customers [Member]
Revenue, Major Customer [Line Items]
Amount	$ 74,275,000	$ 59,749,000	$ 64,855,000
% of Sales (in hundredths)	10.50%	9.30%	8.20%