Goodwill and Intangible Assets (Schedule of Goodwill and Intangible Assets) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Goodwill and Intangible Assets [Roll Forward]
Total goodwill, beginning of period	$ 109,639	$ 95,519	$ 95,519
Established through acquisitions	5,915	14,120	0
Total goodwill, end of period	115,554	109,639	95,519
Core deposit intangible, net, beginning of period	18,696
Total core deposit intangible, end of period	20,166	18,696
Total goodwill and intangible assets, end of period	135,720	128,335	100,382
Core Deposits [Member]
Goodwill and Intangible Assets [Roll Forward]
Gross core deposit intangible balance, beginning of period	26,652	8,896	8,896
Accumulated amortization, beginning of period	(7,956)	(4,033)	(2,988)
Core deposit intangible, net, beginning of period	18,696	4,863	5,908
Established through acquisitions	5,789	17,755	0
CDI current period amortization	(4,319)	(3,922)	(1,045)
Total core deposit intangible, end of period	$ 20,166	$ 18,696	$ 4,863
Estimated life of CDI, in years	10