Consolidated Statements of Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Interest Income
Interest and fees on loans	$ 742,739	$ 685,911	$ 633,199
Interest and dividends on investment securities:
Taxable	72,676	58,143	52,050
Tax-exempt	15,399	15,537	14,568
Dividends	9,812	6,206	6,557
Interest on federal funds sold and other short-term investments	1,793	1,126	649
Total interest income	842,419	766,923	707,023
Interest on deposits:
Savings, NOW and money market	55,300	39,787	24,824
Time	42,546	37,775	35,432
Interest on short-term borrowings	18,034	12,022	919
Interest on long-term borrowings and junior subordinated debentures	58,227	59,190	95,579
Total interest expense	174,107	148,774	156,754
Net Interest Income	668,312	618,149	550,269
Provision for credit losses	9,942	11,869	8,101
Net Interest Income After Provision for Credit Losses	658,370	606,280	542,168
Non-Interest Income
Trust and investment services	11,538	10,345	10,020
Insurance commissions	18,156	19,106	17,233
Service charges on deposit accounts	21,529	20,879	21,176
(Losses) gains on securities transactions, net	(20)	777	2,487
Fees from loan servicing	7,384	6,441	6,641
Gains on sales of loans, net	20,814	22,030	4,245
Bank owned life insurance	7,338	6,694	6,815
Other	16,702	16,953	15,185
Total non-interest income	103,441	103,225	83,802
Non-Interest Expense
Salary and employee benefits expense	254,569	235,853	221,765
Net occupancy and equipment expense	92,243	87,140	90,521
FDIC insurance assessment	19,821	20,100	16,867
Amortization of other intangible assets	10,016	11,327	9,169
Professional and legal fees	25,834	17,755	18,945
Loss on extinguishment of debt	0	315	51,129
Amortization of tax credit investments	41,747	34,744	27,312
Telecommunication expenses	9,921	10,021	8,259
Other	54,922	58,870	55,108
Total non-interest expense	509,073	476,125	499,075
Income Before Income Taxes	252,738	233,380	126,895
Income tax expense	90,831	65,234	23,938
Net Income	161,907	168,146	102,957
Dividends on preferred stock	9,449	7,188	3,813
Net Income Available to Common Shareholders	$ 152,458	$ 160,958	$ 99,144
Earnings Per Common Share:
Basic (in usd per share)	$ 0.58	$ 0.63	$ 0.42
Diluted (in usd per share)	0.58	0.63	0.42
Cash dividends declared per common share (in usd per share)	$ 0.44	$ 0.44	$ 0.44
Weighted Average Number of Common Shares Outstanding:
Basic (in shares)	264,038,123	254,841,571	234,405,909
Diluted (in shares)	264,889,007	255,268,336	234,437,000