Goodwill (Details 1) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011
Gross carrying value of goodwill and the accumulated impairment charge
Gross carrying value	$ 159,668		$ 146,259
Accumulated impairment charge	(40,159)		(40,159)
Net carrying value	$ 119,509	$ 106,100	$ 106,100	$ 106,100	$ 106,100	$ 106,100

Carrying amount as of the balance sheet date, which is the cumulative amount paid and (if applicable) the fair value of any noncontrolling interest in the acquiree, adjusted for any amortization recognized prior to the adoption of any changes in generally accepted accounting principles (as applicable) and for any impairment charges, in excess of the fair value of net assets acquired in one or more business combination transactions.

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