Goodwill and Other Intangible Assets - Components of Goodwill (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012	Dec. 31, 2011
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill	$ 61,152	$ 55,081
Accumulated impairment	(1,988)	(1,988)
Goodwill	$ 59,164	$ 53,093	$ 8,244