Goodwill and Intangible Assets (Details Textual) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2011 Segment	Dec. 31, 2010	Dec. 31, 2009
Goodwill and Intangible Assets (Textual)
Goodwill impairment charges	$ 0	$ 0	$ 0
Number of reportable segments	4
Impairment of intangible assets	$ 0	$ 0	$ 0
Maximum total debt as a percentage of total capital	65.00%
Total debt as a percentage of total capital	42.60%	40.70%

Loss recognized during the period that results from the write-down of goodwill after comparing the implied fair value of reporting unit goodwill with the carrying amount of that goodwill. Goodwill is assessed at least annually for impairment.

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+ Details