Goodwill and Other Intangible Assets - (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2016 USD ($)
Goodwill [Roll Forward]
Balance at January 1, 2016	$ 445,871
Addition to goodwill from Heritage acquisition	3,554
Adjustment to previously recorded goodwill	0
Balance at March 31, 2016	449,425
Community Banks
Goodwill [Roll Forward]
Balance at January 1, 2016	443,104
Addition to goodwill from Heritage acquisition	3,554
Adjustment to previously recorded goodwill	0
Balance at March 31, 2016	446,658
Insurance
Goodwill [Roll Forward]
Balance at January 1, 2016	2,767
Addition to goodwill from Heritage acquisition	0
Adjustment to previously recorded goodwill	0
Balance at March 31, 2016	$ 2,767