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Acquisitions (Details) $ in Thousands		6 Months Ended	12 Months Ended
Acquisitions (Details) $ in Thousands	Oct. 17, 2014 item	Jun. 30, 2015 USD ($)	Dec. 31, 2014 USD ($)	Sep. 30, 2014 USD ($)	Jun. 30, 2014 USD ($)	Dec. 31, 2013 USD ($)
ACQUISITIONS
Assets		$ 2,408,951	$ 2,196,135
Deposit		2,024,531	1,845,713
Loans And Leases Receivable Net Of Allowance		1,877,737	1,784,123
Stockholders' equity		298,652	288,405		$ 208,752	$ 199,218
Goodwill, initial amount recognized			14,457
Finite-lived Intangible Assets Acquired			$ 3,467
SP Bancorp Inc And Its Wholly Owned Subsidiary Share Plus Bank [Member]
ACQUISITIONS
Number of branches \| item	4
Assets				$ 348,700
Deposit				280,500
Loans And Leases Receivable Net Of Allowance				248,200
Stockholders' equity				$ 33,700
Cash paid for entity acquired		46,400
Goodwill, initial amount recognized		14,500
Core deposit intangibles.		$ 3,500
Core deposit intangibles \| Minimum
ACQUISITIONS
Finite-Lived Intangible Asset, Useful Life		6 years
Core deposit intangibles \| Maximum
ACQUISITIONS
Finite-Lived Intangible Asset, Useful Life		16 years
Plano Texas \| SP Bancorp Inc And Its Wholly Owned Subsidiary Share Plus Bank [Member]
ACQUISITIONS
Number of branches \| item	2
Dallas Texas [Member] \| SP Bancorp Inc And Its Wholly Owned Subsidiary Share Plus Bank [Member]
ACQUISITIONS
Number of branches \| item	1
Louisville, Kentucky \| SP Bancorp Inc And Its Wholly Owned Subsidiary Share Plus Bank [Member]
ACQUISITIONS
Number of branches \| item	1