Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Statement of Financial Position [Abstract]
Allowance for trade and other receivables	$ 629	$ 535
Accumulated amortization of intangible assets	$ 227,883	$ 263,305
Common Stock, Shares Authorized	150,000,000	150,000,000
Common Stock, Shares, Issued	47,756,973	47,413,789
Common Stock, Par or Stated Value Per Share	$ 0.01	$ 0.01