Goodwill and Other Intangible Assets (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended			12 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012 Core Deposits Member	Dec. 31, 2011 Core Deposits Member	Sep. 30, 2012 Other Intangible Assets [Member]	Dec. 31, 2011 Other Intangible Assets [Member]
Summary of core deposit intangibles and other intangibles
Gross carrying amount					$ 41,831	$ 41,831	$ 19,283	$ 19,283
Accumulated amortization					(33,237)	(30,815)	(11,601)	(10,877)
Net book value					8,594	11,016	7,682	8,406
Amortization of other intangible assets	$ 1,048	$ 1,179	$ 3,146	$ 3,535	$ 2,422	$ 3,695	$ 724	$ 1,019