Goodwill and Intangible Assets (Schedule of Goodwill and Intangible Assets) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012 Y	Jun. 30, 2011	Mar. 31, 2012	Dec. 31, 2011	Mar. 31, 2011	Dec. 31, 2010
Goodwill and Intangible Assets [Roll Forward]
Total goodwill, beginning of period	$ 115,554	$ 109,639	$ 115,554	$ 109,639
Established through acquisitions	0	9,704	0	9,704
Total goodwill, end of period	115,554	119,343	115,554	119,343
Core deposit intangible, net, beginning of period			20,166
Total goodwill and intangible assets, end of period	133,450	137,945	133,450	137,945
Total core deposit intangible, end of period	17,896		17,896
Core Deposits [Member]
Goodwill and Intangible Assets [Line Items]
Estimated life of CDI, in years			10
Goodwill and Intangible Assets [Roll Forward]
Gross core deposit intangible balance, beginning of period					32,441	32,441	26,651	26,651
Accumulated amortization at beginning of period					(13,425)	(12,275)	(8,939)	(7,955)
Core deposit intangible, net, beginning of period	19,016	17,712	20,166	18,696
Established through acquisitions	0	1,846	0	1,846
CDI current period amortization	(1,120)	(956)	(2,270)	(1,940)
Total core deposit intangible, end of period	$ 17,896	$ 18,602	$ 17,896	$ 18,602