Loans - Summary of Loans (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Summary of loans under portfolio
Total loans	$ 13,273,392	$ 12,990,779
Deferred income	15,000	14,800
Commercial loan portfolio
Summary of loans under portfolio
Total loans	7,805,190	7,594,212
Commercial loan portfolio | Commercial
Summary of loans under portfolio
Total loans	3,253,608	3,217,300
Commercial loan portfolio | Commercial real estate
Summary of loans under portfolio
Total loans	4,097,771	3,973,140
Commercial loan portfolio | Real estate construction and land development
Summary of loans under portfolio
Total loans	453,811	403,772
Consumer loan portfolio
Summary of loans under portfolio
Total loans	5,468,202	5,396,567
Consumer loan portfolio | Residential mortgage
Summary of loans under portfolio
Total loans	3,133,465	3,086,474
Consumer loan portfolio | Consumer installment
Summary of loans under portfolio
Total loans	1,481,057	1,433,884
Consumer loan portfolio | Home equity
Summary of loans under portfolio
Total loans	853,680	876,209
Originated
Summary of loans under portfolio
Total loans	7,959,769	7,458,401
Originated | Commercial
Summary of loans under portfolio
Total loans	1,989,609	1,901,526
Originated | Commercial real estate
Summary of loans under portfolio
Total loans	2,114,540	1,921,799
Originated | Real estate construction and land development
Summary of loans under portfolio
Total loans	327,740	281,724
Originated | Residential mortgage
Summary of loans under portfolio
Total loans	1,594,376	1,475,342
Originated | Consumer installment
Summary of loans under portfolio
Total loans	1,342,063	1,282,588
Originated | Home equity
Summary of loans under portfolio
Total loans	591,441	595,422
Originated | Commercial loan portfolio
Summary of loans under portfolio
Total loans	4,431,889	4,105,049
Originated | Commercial loan portfolio | Commercial
Summary of loans under portfolio
Total loans	1,989,609	1,901,526
Originated | Commercial loan portfolio | Commercial real estate
Summary of loans under portfolio
Total loans	2,114,540	1,921,799
Originated | Commercial loan portfolio | Real estate construction and land development
Summary of loans under portfolio
Total loans	327,740	281,724
Originated | Consumer loan portfolio
Summary of loans under portfolio
Total loans	3,527,880	3,353,352
Originated | Consumer loan portfolio | Residential mortgage
Summary of loans under portfolio
Total loans	1,594,376	1,475,342
Originated | Consumer loan portfolio | Consumer installment
Summary of loans under portfolio
Total loans	1,342,063	1,282,588
Originated | Consumer loan portfolio | Home equity
Summary of loans under portfolio
Total loans	591,441	595,422
Acquired
Summary of loans under portfolio
Total loans	5,313,623	5,532,378
Acquired | Commercial loan portfolio
Summary of loans under portfolio
Total loans	3,373,301	3,489,163
Acquired | Commercial loan portfolio | Commercial
Summary of loans under portfolio
Total loans	1,263,999	1,315,774
Acquired | Commercial loan portfolio | Commercial real estate
Summary of loans under portfolio
Total loans	1,983,231	2,051,341
Acquired | Commercial loan portfolio | Real estate construction and land development
Summary of loans under portfolio
Total loans	126,071	122,048
Acquired | Consumer loan portfolio
Summary of loans under portfolio
Total loans	1,940,322	2,043,215
Acquired | Consumer loan portfolio | Residential mortgage
Summary of loans under portfolio
Total loans	1,539,089	1,611,132
Acquired | Consumer loan portfolio | Consumer installment
Summary of loans under portfolio
Total loans	138,994	151,296
Acquired | Consumer loan portfolio | Home equity
Summary of loans under portfolio
Total loans	$ 262,239	$ 280,787