Goodwill and Other Intangible Assets Summary of Core Deposit and Other Intangibles (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Summary of core deposit intangibles and other intangibles
Amortization of other intangible assets	$ 3,747us-gaap_AmortizationOfIntangibleAssets	$ 4,043us-gaap_AmortizationOfIntangibleAssets	$ 4,195us-gaap_AmortizationOfIntangibleAssets
Core Deposits [Member]
Summary of core deposit intangibles and other intangibles
Gross carrying amount	36,230	36,230	41,831
Accumulated amortization	(34,433)	(31,565)	(34,044)
Total Estimated Amortization Expense	1,797	4,665	7,787
Amortization of other intangible assets	2,868	3,122	3,229
Other Intangible Assets [Member]
Summary of core deposit intangibles and other intangibles
Gross carrying amount	19,283	19,283	19,283
Accumulated amortization	(13,643)	(12,764)	(11,843)
Total Estimated Amortization Expense	5,640	6,519	7,440
Amortization of other intangible assets	$ 879	$ 921	$ 966

The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

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