Loans and Allowance for Loan Losses - (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016
Loans and Allowance for Loan Losses
Loans, net	$ 10,778,068		$ 10,575,417	$ 8,140,706
Non-acquired loans
Loans and Allowance for Loan Losses
Total loans	7,197,539		6,492,155	5,992,393
Less allowance for non-acquired loan losses	(47,874)	$ (45,203)	(43,448)	(40,149)	$ (38,449)	$ (36,960)
Loans, net	7,149,665		6,448,707	5,952,244
Acquired credit impaired loans
Loans and Allowance for Loan Losses
Total loans	556,405		623,430	606,222
Acquired non-credit impaired loans
Loans and Allowance for Loan Losses
Total loans	3,076,424		3,507,907	1,585,981
Acquired non-credit impaired loans | Consumer Owner Occupied Loans
Loans and Allowance for Loan Losses
Total loans				221,566
Residential real estate | Acquired credit impaired loans
Loans and Allowance for Loan Losses
Total loans	229,502		260,787	256,602
Commercial non-owner occupied real estate | Non-acquired loans
Loans and Allowance for Loan Losses
Total loans	2,042,125		1,839,768	1,665,153
Commercial non-owner occupied real estate | Non-acquired loans | Construction and land development
Loans and Allowance for Loan Losses
Total loans	906,890		830,875	712,242
Less allowance for non-acquired loan losses	(6,187)	(5,847)	(5,921)	(5,746)	(4,649)	(4,091)
Commercial non-owner occupied real estate | Non-acquired loans | Other commercial non-owner occupied real estate
Loans and Allowance for Loan Losses
Total loans	1,135,235		1,008,893	952,911
Less allowance for non-acquired loan losses	(7,209)	(6,798)	(6,525)	(6,164)	(5,464)	(4,980)
Commercial non-owner occupied real estate | Acquired credit impaired loans | Construction and land development
Loans and Allowance for Loan Losses
Total loans	40,951		49,649	52,977
Commercial non-owner occupied real estate | Acquired credit impaired loans | Other commercial non-owner occupied real estate
Loans and Allowance for Loan Losses
Total loans	227,739		234,595	214,795
Commercial non-owner occupied real estate | Acquired non-credit impaired loans | Construction and land development
Loans and Allowance for Loan Losses
Total loans	281,282		403,357
Commercial non-owner occupied real estate | Acquired non-credit impaired loans | Other commercial non-owner occupied real estate
Loans and Allowance for Loan Losses
Total loans	752,465		817,166	209,560
Commercial owner occupied real estate loan | Non-acquired loans
Loans and Allowance for Loan Losses
Total loans	1,372,453		1,262,776	1,204,953
Less allowance for non-acquired loan losses	(8,607)	(8,346)	(8,128)	(7,539)	(7,894)	(8,022)
Commercial owner occupied real estate loan | Non-acquired loans | Home equity loans
Loans and Allowance for Loan Losses
Less allowance for non-acquired loan losses	(3,368)		(3,250)	(3,247)		(3,211)
Commercial owner occupied real estate loan | Acquired non-credit impaired loans
Loans and Allowance for Loan Losses
Total loans	486,254		521,818
Consumer real estate | Non-acquired loans
Loans and Allowance for Loan Losses
Total loans	2,190,870		1,967,902	1,794,454
Consumer real estate | Non-acquired loans | Home equity loans
Loans and Allowance for Loan Losses
Total loans	456,946		437,642	411,532
Less allowance for non-acquired loan losses	(3,368)	(3,237)		(3,247)	(3,456)
Consumer real estate | Non-acquired loans | Consumer Owner Occupied Loans
Loans and Allowance for Loan Losses
Total loans	1,733,924		1,530,260	1,382,922
Less allowance for non-acquired loan losses	(10,945)	(10,193)	(9,668)	(8,569)	(8,108)	(7,820)
Consumer real estate | Acquired non-credit impaired loans | Home equity loans
Loans and Allowance for Loan Losses
Total loans	278,906		320,591	177,129
Consumer real estate | Acquired non-credit impaired loans | Consumer Owner Occupied Loans
Loans and Allowance for Loan Losses
Total loans	676,596		710,611	520,106
Commercial and industrial | Non-acquired loans
Loans and Allowance for Loan Losses
Total loans	941,067		815,187	762,583
Less allowance for non-acquired loan losses	(6,711)	(6,333)	(5,488)	(5,143)	(5,124)	(4,842)
Commercial and industrial | Acquired credit impaired loans
Loans and Allowance for Loan Losses
Total loans	12,580		26,946	25,486
Commercial and industrial | Acquired non-credit impaired loans
Loans and Allowance for Loan Losses
Total loans	304,864		398,696	117,884
Commercial and industrial | Acquired non-credit impaired loans | Construction and land development
Loans and Allowance for Loan Losses
Total loans				112,855
Commercial and industrial | Acquired non-credit impaired loans | Home equity loans
Loans and Allowance for Loan Losses
Total loans				117,884
Other income producing property | Non-acquired loans
Loans and Allowance for Loan Losses
Total loans	205,507		193,847	189,326
Less allowance for non-acquired loan losses	(1,413)	(1,393)	(1,375)	(1,379)	(1,345)	(1,542)
Other income producing property | Acquired non-credit impaired loans
Loans and Allowance for Loan Losses
Total loans	169,392		196,669	83,403
Consumer | Non-acquired loans
Loans and Allowance for Loan Losses
Total loans	416,650		378,985	357,761
Less allowance for non-acquired loan losses	(3,071)	(2,899)	(2,788)	(2,532)	(2,443)	(2,350)
Consumer | Non-acquired loans | Consumer
Loans and Allowance for Loan Losses
Total loans	416,650		378,985	357,761
Consumer | Acquired credit impaired loans
Loans and Allowance for Loan Losses
Total loans	45,633		51,453	56,362
Consumer | Acquired non-credit impaired loans
Loans and Allowance for Loan Losses
Total loans	126,665		137,710	143,478
Commercial | Non-acquired loans
Loans and Allowance for Loan Losses
Total loans	4,561,152		4,111,578	3,822,015
Commercial | Acquired non-credit impaired loans | Construction and land development
Loans and Allowance for Loan Losses
Total loans	281,282			112,855
Commercial | Acquired non-credit impaired loans | Other commercial non-owner occupied real estate
Loans and Allowance for Loan Losses
Total loans	486,254			221,566
Other loans | Non-acquired loans
Loans and Allowance for Loan Losses
Total loans	28,867		33,690	18,163
Less allowance for non-acquired loan losses	$ (363)	$ (157)	(305)	$ 170	$ 34	$ (102)
Other loans | Acquired non-credit impaired loans
Loans and Allowance for Loan Losses
Total loans			$ 1,289