Net Carrying Value of Goodwill (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Jun. 30, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Dec. 31, 2011
Gross carrying value of goodwill and the accumulated impairment charge
Gross carrying value	$ 169,865		$ 146,259
Accumulated impairment charge	(40,159)		(40,159)
Net carrying value	$ 129,706	$ 119,509	$ 106,100	$ 106,100	$ 106,100	$ 106,100

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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