Intangible Assets (Amortization Expense of Core Deposit Intangible Assets) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
Carrying amount, accumulated amortization and amortization expense of core deposit intangible assets
Carrying amount	$ 14,902	$ 10,939	$ 15,388
Amortization of intangible assets	1,001	1,067
Core deposit intangible assets [Member]
Carrying amount, accumulated amortization and amortization expense of core deposit intangible assets
Gross original amount	18,659	26,468	18,659
Accumulated amortization	7,242	18,956	6,749
Carrying amount	11,417	7,512	11,910
Amortization of intangible assets	$ 493	$ 367