Income Taxes (Effective Income Tax Rate Reconciliation) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Taxes computed at statutory rate, amount	$ 107,952	$ 65,423	$ 59,418
State income taxes, net of federal income tax benefit, amount	4,737	1,917	2,595
Tax-exempt interest, amount	(18,870)	(14,497)	(7,849)
Life insurance contracts	(5,360)	(4,833)	(3,798)
Tax credits, amount	(9,374)	(10,518)	(12,495)
Employee share-based compensation	(5,824)
Impact of deferred tax asset re-measurement	19,520
Other, net, amount	21	135	433
Total included in net income	$ 92,802	$ 37,627	$ 38,304
Taxes computed at statutory rate	35.00%	35.00%	35.00%
State income taxes, net of federal income tax benefit	1.50%	1.00%	1.50%
Tax-exempt interest	(6.10%)	(7.80%)	(4.60%)
Life insurance contracts	(1.70%)	(2.60%)	(2.20%)
Tax credits	(3.00%)	(5.60%)	(7.40%)
Employee share-based compensation	(1.90%)
Impact of deferred tax asset re-measurement	6.30%
Other, net		0.10%	0.30%
Income tax expense	30.10%	20.10%	22.60%
Hancock Holding Company [Member]
Total included in net income	$ (6,324)	$ (6,617)	$ (6,334)