Intangible Assets (Narrative) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Intangible Assets [Abstract]
Costs incurred to acquire, develop and extend patents	$ 177	$ 231
Amortization expense for intangible assets	3,812	3,419
Annual estimated amortization expense, in 2013	16,373
Annual estimated amortization expense, in 2014	16,841
Annual estimated amortization expense, in 2015	15,263
Annual estimated amortization expense, in 2016	13,261
Annual estimated amortization expense, in 2017	$ 12,006