Acquisitions - Schedule of Preliminary Purchase Price Allocation (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	May 30, 2014
Business Acquisition [Line Items]
Loans	$ 10,987,535	$ 9,515,700
Goodwill	653,950us-gaap_Goodwill	536,649us-gaap_Goodwill
Deposits	(24,135,930)us-gaap_Deposits	(20,688,786)us-gaap_Deposits
WNB Bancshares, Inc. [Member]
Business Acquisition [Line Items]
Cash and equivalents			879,740
Securities available for sale			154,227
Loans			670,619
Premises and equipment			22,853
Core deposit intangible assets			9,300
Goodwill			117,301
Other assets			33,644
Deposits			(1,624,043)
Other borrowings			(63,592)
Other liabilities			(1,251)
Preliminary purchase price allocation			$ 198,798

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Amount of currency on hand as well as demand deposits with banks or financial institutions, acquired at the acquisition date. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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Amount of investments in debt and equity securities, including, but not limited to, held-to-maturity, trading and available-for-sale expected to be converted to cash, sold or exchanged within one year or the normal operating cycle, if longer, acquired at the acquisition date.

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Amount of other liabilities due within one year or within the normal operating cycle, if longer, assumed at the acquisition date.

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The amount of financial liabilities assumed (as defined) which have been recognized as of the acquisition date.

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Amount of intangible assets, excluding goodwill, acquired at the acquisition date.

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Amount recognized as of the acquisition date for the identifiable assets acquired in excess of (less than) the aggregate liabilities assumed.

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Amount of other assets expected to be realized or consumed after one year or the normal operating cycle, if longer, acquired at the acquisition date.

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The amount of property, plant, and equipment recognized as of the acquisition date.

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The aggregate of all deposit liabilities held by the entity, including foreign and domestic, interest and noninterest bearing; may include demand deposits, saving deposits, Negotiable Order of Withdrawal (NOW) and time deposits among others.

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Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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Amount before allowance and after deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements.

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