Goodwill and Intangible Assets (Schedule of Goodwill and Intangible Assets) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Goodwill and Intangible Assets [Roll Forward]
Total goodwill, beginning of period	$ 115,554	$ 109,639	$ 95,519
Established through acquisitions	0	5,915	14,120
Total goodwill, end of period	115,554	115,554	109,639
Core deposit intangible, net, beginning of period	20,166
CDI current period amortization	(4,445)	(4,319)	(3,922)
Total core deposit intangible, end of period	15,721	20,166
Total goodwill and intangible assets, end of period	131,275	135,720	128,335
Core Deposits [Member]
Goodwill and Intangible Assets [Roll Forward]
Gross core deposit intangible balance, beginning of period	32,441	26,652	8,896
Accumulated amortization, beginning of period	(12,275)	(7,956)	(4,033)
Core deposit intangible, net, beginning of period	20,166	18,696	4,863
Established through acquisitions	0	5,789	17,755
CDI current period amortization	(4,445)	(4,319)	(3,922)
Total core deposit intangible, end of period	$ 15,721	$ 20,166	$ 18,696
Estimated life of CDI, in years	10 years