Loans - Summary of Loans (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Summary of loans under portfolio
Total loans	$ 13,667,372	$ 12,990,779
Deferred income	20,000	14,800
Commercial loan portfolio
Summary of loans under portfolio
Total loans	8,131,162	7,594,212
Commercial loan portfolio | Commercial
Summary of loans under portfolio
Total loans	3,360,161	3,217,300
Commercial loan portfolio | Commercial real estate
Summary of loans under portfolio
Total loans	4,324,323	3,973,140
Commercial loan portfolio | Real estate construction and land development
Summary of loans under portfolio
Total loans	446,678	403,772
Consumer loan portfolio
Summary of loans under portfolio
Total loans	5,536,210	5,396,567
Consumer loan portfolio | Residential mortgage
Summary of loans under portfolio
Total loans	3,125,397	3,086,474
Consumer loan portfolio | Consumer installment
Summary of loans under portfolio
Total loans	1,553,967	1,433,884
Consumer loan portfolio | Home equity
Summary of loans under portfolio
Total loans	856,846	876,209
Originated
Summary of loans under portfolio
Total loans	8,659,622	7,458,401
Originated | Commercial
Summary of loans under portfolio
Total loans	2,184,283	1,901,526
Originated | Commercial real estate
Summary of loans under portfolio
Total loans	2,405,772	1,921,799
Originated | Real estate construction and land development
Summary of loans under portfolio
Total loans	349,395	281,724
Originated | Residential mortgage
Summary of loans under portfolio
Total loans	1,683,550	1,475,342
Originated | Consumer installment
Summary of loans under portfolio
Total loans	1,429,088	1,282,588
Originated | Home equity
Summary of loans under portfolio
Total loans	607,534	595,422
Originated | Commercial loan portfolio
Summary of loans under portfolio
Total loans	4,939,450	4,105,049
Originated | Commercial loan portfolio | Commercial
Summary of loans under portfolio
Total loans	2,184,283	1,901,526
Originated | Commercial loan portfolio | Commercial real estate
Summary of loans under portfolio
Total loans	2,405,772	1,921,799
Originated | Commercial loan portfolio | Real estate construction and land development
Summary of loans under portfolio
Total loans	349,395	281,724
Originated | Consumer loan portfolio
Summary of loans under portfolio
Total loans	3,720,172	3,353,352
Originated | Consumer loan portfolio | Residential mortgage
Summary of loans under portfolio
Total loans	1,683,550	1,475,342
Originated | Consumer loan portfolio | Consumer installment
Summary of loans under portfolio
Total loans	1,429,088	1,282,588
Originated | Consumer loan portfolio | Home equity
Summary of loans under portfolio
Total loans	607,534	595,422
Acquired
Summary of loans under portfolio
Total loans	5,007,750	5,532,378
Acquired | Commercial loan portfolio
Summary of loans under portfolio
Total loans	3,191,712	3,489,163
Acquired | Commercial loan portfolio | Commercial
Summary of loans under portfolio
Total loans	1,175,878	1,315,774
Acquired | Commercial loan portfolio | Commercial real estate
Summary of loans under portfolio
Total loans	1,918,551	2,051,341
Acquired | Commercial loan portfolio | Real estate construction and land development
Summary of loans under portfolio
Total loans	97,283	122,048
Acquired | Consumer loan portfolio
Summary of loans under portfolio
Total loans	1,816,038	2,043,215
Acquired | Consumer loan portfolio | Residential mortgage
Summary of loans under portfolio
Total loans	1,441,847	1,611,132
Acquired | Consumer loan portfolio | Consumer installment
Summary of loans under portfolio
Total loans	124,879	151,296
Acquired | Consumer loan portfolio | Home equity
Summary of loans under portfolio
Total loans	$ 249,312	$ 280,787