Parent Company Only Financial Information, Statement of Cash Flows (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	$ 200,274	$ 188,301	$ 190,509
Adjustments to reconcile net income to net cash provided by operating activities:
Gain on sales of investment securities, net	(9,316)	(8,133)	(494)
Asset (gains) losses, net	86	(2,540)	(10,830)
Net change in other assets and other liabilities	21,915	(9,565)	(3,661)
Net cash provided by operating activities	628,942	301,744	199,509
CASH FLOWS FROM INVESTING ACTIVITIES
Proceeds from sales of investment securities	549,555	1,601,947	102,011
Net cash used in investing activities	(1,640,582)	(1,534,356)	(2,118,605)
CASH FLOWS FROM FINANCING ACTIVITIES
Net increase (decrease) in short-term funding	257,619	(233,872)	327,362
Repayment of long-term funding	(1,180,038)	(1,500,035)	(155,066)
Proceeds from issuance of long-term funding	1,265,000	250,000	996,030
Proceeds from issuance of common stock for stock-based compensation plans	21,748	20,054	13,228
Proceeds from issuance of preferred shares	97,066	62,966	0
Redemption of preferred stock	58,903	0	0
Purchase of preferred stock	(1,248)	(1,335)	(2,451)
Purchase of common stock returned to authorized but unissued	(20,007)	(93,000)	(150,498)
Purchase of treasury stock	0	0	(108,600)
payments for repurchase of common stock for tax withholding	5,074	5,154	3,712
Payments of Ordinary Dividends, Common Stock	67,855	62,400	58,710
Payments of Ordinary Dividends, Preferred Stock and Preference Stock	8,903	7,155	5,002
Net cash provided by financing activities	1,180,188	674,230	2,348,918
Net increase (decrease) in cash and cash equivalents	168,548	(558,382)	429,822
Cash and cash equivalents at beginning of period	473,685	1,032,067	602,245
Cash and cash equivalents at end of period	642,233	473,685	1,032,067
Associated Banc-Corp
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	200,274	188,301	190,509
Adjustments to reconcile net income to net cash provided by operating activities:
(Increase) decrease in equity in undistributed net income of subsidiaries	(37,263)	(17,455)	23,646
Gain on sales of investment securities, net	(466)	0	(214)
Asset (gains) losses, net	(793)	(5,673)	(5,609)
Net change in other assets and other liabilities	19,708	(10,997)	(14,022)
Net cash provided by operating activities	181,460	154,176	194,310
CASH FLOWS FROM INVESTING ACTIVITIES
Proceeds from sales of investment securities	47,719	13,962	88,844
Net decrease in notes receivable	0	0	46,594
Purchase of other assets, net of disposals	2,211	11,964	10,930
Net cash used in investing activities	49,930	25,926	146,368
CASH FLOWS FROM FINANCING ACTIVITIES
Net increase (decrease) in short-term funding	33,710	(6,319)	8,813
Repayment of long-term funding	(430,000)	0	(155,000)
Proceeds from issuance of long-term funding	0	0	496,030
Proceeds from issuance of common stock for stock-based compensation plans	21,748	20,054	13,228
Proceeds from issuance of preferred shares	97,066	62,966	0
Redemption of preferred stock	(58,903)	0	0
Purchase of preferred stock	(1,248)	(1,335)	(2,451)
Purchase of common stock returned to authorized but unissued	(20,007)	(93,000)	(150,498)
Purchase of treasury stock	0	0	(108,600)
payments for repurchase of common stock for tax withholding	5,074	5,154	3,712
Payments of Ordinary Dividends, Common Stock	(67,855)	(62,400)	(58,710)
Payments of Ordinary Dividends, Preferred Stock and Preference Stock	(8,903)	(7,155)	(5,002)
Net cash provided by financing activities	(439,466)	(92,343)	34,098
Net increase (decrease) in cash and cash equivalents	(208,076)	87,759	374,776
Cash and cash equivalents at beginning of period	610,862	523,103	148,327
Cash and cash equivalents at end of period	$ 402,786	$ 610,862	$ 523,103