Loans and Allowance for Loan Losses - (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Jun. 30, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Dec. 31, 2015
Loans and Allowance for Loan Losses
Loans, net	$ 8,223,204		$ 6,643,326	$ 6,489,068
Non-acquired loans
Loans and Allowance for Loan Losses
Total loans	6,230,327		5,241,041	5,008,113
Less allowance for non-acquired loan losses	(41,541)	$ (40,149)	(36,960)	(37,319)	$ (36,939)	$ (34,090)
Loans, net	6,188,786		5,204,081	4,970,794
Non-acquired loans | Other commercial non-owner occupied real estate
Loans and Allowance for Loan Losses
Less allowance for non-acquired loan losses	(6,237)		(4,980)	(4,591)		(3,568)
Non-acquired loans | Consumer Owner Occupied Loans
Loans and Allowance for Loan Losses
Less allowance for non-acquired loan losses	(8,110)		(8,022)	(8,528)		(8,341)
Acquired credit impaired loans
Loans and Allowance for Loan Losses
Total loans	582,533			636,020
Acquired non-credit impaired loans
Loans and Allowance for Loan Losses
Total loans	1,455,555			885,657
Residential real estate | Acquired credit impaired loans
Loans and Allowance for Loan Losses
Total loans	249,666			268,968
Commercial non-owner occupied real estate | Non-acquired loans
Loans and Allowance for Loan Losses
Total loans	1,716,827		1,295,179	1,192,773
Commercial non-owner occupied real estate | Non-acquired loans | Construction and land development
Loans and Allowance for Loan Losses
Total loans	766,957		580,464	562,336
Less allowance for non-acquired loan losses	(5,972)	(5,746)		(4,111)	(4,665)
Commercial non-owner occupied real estate | Non-acquired loans | Other commercial non-owner occupied real estate
Loans and Allowance for Loan Losses
Total loans	949,870		714,715	630,437
Less allowance for non-acquired loan losses	(6,237)	(6,164)		(4,591)	(4,656)
Commercial non-owner occupied real estate | Acquired credit impaired loans | Construction and land development
Loans and Allowance for Loan Losses
Total loans	46,248			47,081
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	199,082			220,489
Commercial non-owner occupied real estate | Acquired non-credit impaired loans
Loans and Allowance for Loan Losses
Total loans	199,704			35,775
Commercial non-owner occupied real estate | Acquired non-credit impaired loans | Construction and land development
Loans and Allowance for Loan Losses
Total loans	76,886			10,683
Commercial owner occupied real estate loan | Non-acquired loans
Loans and Allowance for Loan Losses
Total loans	1,278,487		1,177,745	1,153,480
Less allowance for non-acquired loan losses	(8,110)	(7,539)		(8,528)	(8,003)
Commercial owner occupied real estate loan | Acquired non-credit impaired loans
Loans and Allowance for Loan Losses
Total loans	207,572			29,444
Consumer real estate | Non-acquired loans
Loans and Allowance for Loan Losses
Total loans	1,874,518		1,580,839	1,547,266
Consumer real estate | Non-acquired loans | Home equity loans
Loans and Allowance for Loan Losses
Total loans	419,760		383,218	363,825
Less allowance for non-acquired loan losses	(3,097)	(3,247)		(3,281)	(3,148)
Consumer real estate | Non-acquired loans | Consumer
Loans and Allowance for Loan Losses
Total loans	2,258,921		1,918,481	1,864,740
Consumer real estate | Non-acquired loans | Consumer Owner Occupied Loans
Loans and Allowance for Loan Losses
Total loans	1,454,758		1,197,621	1,183,441
Less allowance for non-acquired loan losses	(9,126)	(8,569)		(7,850)	(7,530)
Consumer real estate | Acquired credit impaired loans
Loans and Allowance for Loan Losses
Total loans	53,302			61,866
Consumer real estate | Acquired non-credit impaired loans | Home equity loans
Loans and Allowance for Loan Losses
Total loans	164,291			168,758
Consumer real estate | Acquired non-credit impaired loans | Consumer Owner Occupied Loans
Loans and Allowance for Loan Losses
Total loans	492,615			435,132
Commercial and industrial | Non-acquired loans
Loans and Allowance for Loan Losses
Total loans	781,757		671,398	617,525
Less allowance for non-acquired loan losses	(5,203)	(5,143)	(4,842)	(4,710)	(4,269)	(3,974)
Commercial and industrial | Acquired credit impaired loans
Loans and Allowance for Loan Losses
Total loans	25,796			26,658
Commercial and industrial | Acquired non-credit impaired loans
Loans and Allowance for Loan Losses
Total loans	101,427			14,201
Other income producing property | Non-acquired loans
Loans and Allowance for Loan Losses
Total loans	194,335		178,238	179,595
Less allowance for non-acquired loan losses	(1,388)	(1,379)	(1,542)	(1,619)	(1,812)	(1,963)
Other income producing property | Acquired non-credit impaired loans
Loans and Allowance for Loan Losses
Total loans	76,924			43,152
Consumer | Non-acquired loans
Loans and Allowance for Loan Losses
Total loans	371,758		324,238	305,687
Less allowance for non-acquired loan losses	(2,692)	(2,532)		(2,308)	(2,014)
Consumer | Non-acquired loans | Home equity loans
Loans and Allowance for Loan Losses
Less allowance for non-acquired loan losses	(3,097)		(3,211)	(3,281)		(2,929)
Consumer | Non-acquired loans | Consumer
Loans and Allowance for Loan Losses
Less allowance for non-acquired loan losses	(2,692)		(2,350)	(2,308)		(1,694)
Consumer | Non-acquired loans | Other Consumer
Loans and Allowance for Loan Losses
Less allowance for non-acquired loan losses	284		(102)	(321)		(293)
Consumer | Non-acquired loans | Consumer Owner Occupied Loans
Loans and Allowance for Loan Losses
Less allowance for non-acquired loan losses	(9,126)		(7,820)	(7,850)		(7,212)
Consumer | Acquired non-credit impaired loans
Loans and Allowance for Loan Losses
Total loans	136,136			148,512
Commercial | Non-acquired loans
Loans and Allowance for Loan Losses
Total loans	3,971,406		3,322,560	3,143,373
Commercial | Non-acquired loans | Construction and land development
Loans and Allowance for Loan Losses
Less allowance for non-acquired loan losses	(5,972)		(4,091)	(4,111)		$ (4,116)
Other loans | Non-acquired loans
Loans and Allowance for Loan Losses
Total loans	12,645		$ 13,404	11,787
Less allowance for non-acquired loan losses	284	$ 170		(321)	$ (842)
Commercial loans 1000000 or more | Acquired credit impaired loans
Loans and Allowance for Loan Losses
Total loans	$ 8,439			$ 10,958