Goodwill and Intangible Assets (Schedule of Goodwill and Intangible Assets) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012 years	Mar. 31, 2011	Dec. 31, 2011	Dec. 31, 2010
Goodwill and Intangible Assets [Roll Forward]
Total goodwill, beginning of period			$ 115,554
Total goodwill, end of period	115,554	109,639	115,554
Core deposit intangible, net, beginning of period			20,166
Total core deposit intangible, end of period	19,016		20,166
Total goodwill and intangible assets, end of period	134,570	127,351
Core Deposits [Member]
Goodwill and Intangible Assets [Roll Forward]
Gross core deposit intangible balance, beginning of period			32,441	26,651
Accumulated amortization, beginning of period	(12,275)	(7,955)
Core deposit intangible, net, beginning of period	20,166	18,696
CDI current period amortization	(1,150)	(984)
Total core deposit intangible, end of period	$ 19,016	$ 17,712
Estimated life of CDI, in years	10