Loans and Allowance for Loan Losses - Summary of non acquired loans - (Details) - USD ($)	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Loans and Allowance for Loan Losses
Total loans	$ 1,289,000
Loans, net	10,575,417,000	$ 6,643,326,000
Deferred fees	466,000	341,000,000,000
Non-acquired loans
Loans and Allowance for Loan Losses
Total loans	6,492,155,000	5,241,041,000	$ 4,220,726,000
Less allowance for non-acquired loan losses	(43,448,000)	(36,960,000)	(34,090,000)	$ (34,539,000)
Loans, net	6,448,707,000	5,204,081,000
Commercial non-owner occupied real estate \| Non-acquired loans
Loans and Allowance for Loan Losses
Total loans	1,839,768,000	1,295,179,000
Commercial non-owner occupied real estate \| Construction and land development \| Non-acquired loans
Loans and Allowance for Loan Losses
Total loans	830,875,000	580,464,000	401,979,000
Less allowance for non-acquired loan losses	(5,921,000)	(4,091,000)	(4,116,000)	(5,666,000)
Commercial non-owner occupied real estate \| Other commercial non-owner occupied real estate \| Non-acquired loans
Loans and Allowance for Loan Losses
Total loans	1,008,893,000	714,715,000	487,777,000
Less allowance for non-acquired loan losses	(6,525,000)	(4,980,000)	(3,568,000)	(3,154,000)
Consumer real estate \| Non-acquired loans
Loans and Allowance for Loan Losses
Total loans	1,967,902,000	1,580,839,000
Consumer real estate \| Home equity loans \| Non-acquired loans
Loans and Allowance for Loan Losses
Total loans	437,642,000	383,218,000	319,255,000
Less allowance for non-acquired loan losses	(3,250,000)	(3,211,000)	(2,929,000)	(2,829,000)
Commercial and industrial \| Non-acquired loans
Loans and Allowance for Loan Losses
Total loans	815,187,000	671,398,000	503,808,000
Less allowance for non-acquired loan losses	(5,488,000)	(4,842,000)	(3,974,000)	(3,561,000)
Other income producing property \| Non-acquired loans
Loans and Allowance for Loan Losses
Total loans	193,847,000	178,238,000	175,848,000
Less allowance for non-acquired loan losses	(1,375,000)	(1,542,000)	(1,963,000)	(2,232,000)
Consumer \| Non-acquired loans
Loans and Allowance for Loan Losses
Total loans	378,985,000	324,238,000	233,104,000
Less allowance for non-acquired loan losses	$ (2,788,000)	$ (2,350,000)	$ (1,694,000)	$ (1,367,000)

The amount of deferred fees, net of deferred costs as of the reporting period.

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Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

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

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