Loans (Summary of the Aging Status of the Recorded Investment in Loans by Portfolio Segment/Class) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Schedule representing the aging status of the recorded investment in loans by classes
Total loans	$ 14,155,267	$ 12,990,779
Commercial
Schedule representing the aging status of the recorded investment in loans by classes
Total loans		3,217,300
Commercial real estate
Schedule representing the aging status of the recorded investment in loans by classes
Total loans		3,973,140
Real estate construction and land development
Schedule representing the aging status of the recorded investment in loans by classes
Total loans		403,772
Residential mortgage
Schedule representing the aging status of the recorded investment in loans by classes
Total loans		3,086,474
Consumer installment
Schedule representing the aging status of the recorded investment in loans by classes
Total loans		1,433,884
Home equity
Schedule representing the aging status of the recorded investment in loans by classes
Total loans		876,209
Originated Portfolio
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	58,857	51,633
Current	9,688,572	7,406,768
Total loans	9,747,429	7,458,401
Financing receivable, recorded investment accruing loans past due 90 days or more	1,377	1,283
Originated Portfolio | 30-59 days past due
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	31,724	29,928
Originated Portfolio | 60-89 days past due
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	8,486	8,560
Originated Portfolio | 90 days or more past due
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	18,647	13,145
Originated Portfolio | Commercial
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	27,166	18,904
Current	2,380,440	1,882,622
Total loans	2,407,606	1,901,526
Financing receivable, recorded investment accruing loans past due 90 days or more	0	11
Originated Portfolio | Commercial | 30-59 days past due
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	13,906	10,421
Originated Portfolio | Commercial | 60-89 days past due
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	3,766	4,842
Originated Portfolio | Commercial | 90 days or more past due
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	9,494	3,641
Originated Portfolio | Commercial real estate
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	16,815	13,305
Current	2,734,610	1,908,494
Total loans	2,751,425	1,921,799
Financing receivable, recorded investment accruing loans past due 90 days or more	13	277
Originated Portfolio | Commercial real estate | 30-59 days past due
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	9,380	6,551
Originated Portfolio | Commercial real estate | 60-89 days past due
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	1,562	1,589
Originated Portfolio | Commercial real estate | 90 days or more past due
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	5,873	5,165
Originated Portfolio | Real estate construction and land development
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	0	3,220
Current	498,155	278,504
Total loans	498,155	281,724
Financing receivable, recorded investment accruing loans past due 90 days or more	0	0
Originated Portfolio | Real estate construction and land development | 30-59 days past due
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	0	2,721
Originated Portfolio | Real estate construction and land development | 60-89 days past due
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	0	499
Originated Portfolio | Real estate construction and land development | 90 days or more past due
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	0	0
Originated Portfolio | Residential mortgage
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	5,068	4,961
Current	1,962,789	1,470,381
Total loans	1,967,857	1,475,342
Financing receivable, recorded investment accruing loans past due 90 days or more	0	0
Originated Portfolio | Residential mortgage | 30-59 days past due
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	2,795	3,147
Originated Portfolio | Residential mortgage | 60-89 days past due
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	1,415	62
Originated Portfolio | Residential mortgage | 90 days or more past due
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	858	1,752
Originated Portfolio | Consumer installment
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	3,992	4,904
Current	1,506,548	1,277,684
Total loans	1,510,540	1,282,588
Financing receivable, recorded investment accruing loans past due 90 days or more	0	0
Originated Portfolio | Consumer installment | 30-59 days past due
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	3,324	3,991
Originated Portfolio | Consumer installment | 60-89 days past due
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	442	675
Originated Portfolio | Consumer installment | 90 days or more past due
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	226	238
Originated Portfolio | Home equity
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	5,816	6,339
Current	606,030	589,083
Total loans	611,846	595,422
Financing receivable, recorded investment accruing loans past due 90 days or more	1,364	995
Originated Portfolio | Home equity | 30-59 days past due
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	2,319	3,097
Originated Portfolio | Home equity | 60-89 days past due
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	1,301	893
Originated Portfolio | Home equity | 90 days or more past due
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	$ 2,196	$ 2,349