Acquisitions (Acquisition, fair values) (Details) - USD ($) $ in Thousands	Feb. 05, 2016	Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015
Fair value of liabilities assumed:
Goodwill resulting from acquisition		$ 127,699	$ 97,852
Assets		$ 8,253,779	$ 7,694,754	$ 6,506,276
CIC Bancshares, Inc.
Fair value of consideration paid:
Stock, number of shares	2,003,235
Cash	$ 15,672
Total consideration paid	76,882
Fair value of assets acquired:
Cash and due from banks	23,756
Securities:
Securities available for sale	92,831
Other securities	3,486
Loans held to maturity	581,477
Premises, furniture and equipment, net	16,450
Other real estate, net	1,934
Other intangible assets, net	6,576
Other assets	16,276
Total assets	742,786
Fair value of liabilities assumed:
Deposits	648,111
Short term borrowings	35,766
Other borrowings	7,924
Other liabilities	3,951
Total liabilities assumed	695,752
Fair value of net assets acquired	47,034
Goodwill resulting from acquisition	29,848
Assets	772,600
CIC Bancshares, Inc. | Common Stock
Fair value of consideration paid:
Stock	$ 57,433
Stock, number of shares	2,003,235
CIC Bancshares, Inc. | Preferred Stock
Fair value of consideration paid:
Stock	$ 3,777
Stock, number of shares	3,000