PARENT COMPANY STATEMENTS, Condensed Statements of Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Expenses [Abstract]
Interest on borrowings	$ 2,949	$ 2,537	$ 2,477
Acquisition expenses	1,706	7,037	123
Other expenses	16,553	13,521	17,310
Income before tax benefit and equity in undistributed net income of subsidiaries	154,597	132,217	129,690
Income tax benefit/(expense)	(50,785)	(40,987)	(38,337)
Net income	103,812	91,230	91,353
Other comprehensive (loss)/income, net of tax [Abstract]
Other comprehensive income/(loss) related to pension and other post retirement obligations	3,322	(4,567)	(9,571)
Other comprehensive (loss)/income related to unrealized (losses)/gains on available-for-sale securities	(14,714)	(6,918)	66,837
Other comprehensive (loss)/income, net of tax	(11,392)	(11,485)	57,266
Comprehensive income	92,420	79,745	148,619
Parent Company [Member]
Dividends from subsidiaries [Abstract]
Bank subsidiary	89,000	70,000	57,200
Non-bank subsidiaries	1,750	6,000	3,900
Interest and dividends on investments	102	94	88
Total revenues	90,852	76,094	61,188
Expenses [Abstract]
Interest on borrowings	2,949	2,537	2,477
Acquisition expenses	429	0	0
Other expenses	11	19	37
Total expenses	3,389	2,556	2,514
Income before tax benefit and equity in undistributed net income of subsidiaries	87,463	73,538	58,674
Income tax benefit/(expense)	866	(572)	581
Income before equity in undistributed net income of subsidiaries	88,329	72,966	59,255
Equity in undistributed net income of subsidiaries	15,483	18,264	32,098
Net income	103,812	91,230	91,353
Other comprehensive (loss)/income, net of tax [Abstract]
Other comprehensive income/(loss) related to pension and other post retirement obligations	3,322	(4,567)	(9,571)
Other comprehensive (loss)/income related to unrealized (losses)/gains on available-for-sale securities	(14,714)	(6,918)	66,837
Other comprehensive (loss)/income, net of tax	(11,392)	(11,485)	57,266
Comprehensive income	$ 92,420	$ 79,745	$ 148,619