Junior Subordinated Debentures (Summary Of The Company's Junior Subordinated Debentures) (Detail) (USD $) In Thousands, unless otherwise specified				3 Months Ended
	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013	Mar. 31, 2014 Wintrust Capital Trust III Rate	Mar. 31, 2014 Wintrust Statutory Trust IV Rate	Mar. 31, 2014 Wintrust Statutory Trust V Rate	Mar. 31, 2014 Wintrust Capital Trust VII Rate	Mar. 31, 2014 Wintrust Capital Trust VIII Rate	Mar. 31, 2014 Wintrust Capital Trust IX Rate	Mar. 31, 2014 Northview Capital Trust I Rate	Mar. 31, 2014 Town Bankshares Capital Trust I Rate	Mar. 31, 2014 First Northwest Capital Trust I Rate
Subordinated Borrowing [Line Items]
Common Securities				$ 774	$ 619	$ 1,238	$ 1,550	$ 1,238	$ 1,547	$ 186	$ 186	$ 155
Trust Preferred Securities				25,000	20,000	40,000	50,000	40,000	50,000	6,000	6,000	5,000
Junior subordinated debentures	$ 249,493	$ 249,493	$ 249,493	$ 25,774	$ 20,619	$ 41,238	$ 51,550	$ 41,238	$ 51,547	$ 6,186	$ 6,186	$ 5,155
Rate Structure				L+3.25	L+2.80	L+2.60	L+1.95	L+1.45	L+1.63	L+3.00	L+3.00	L+3.00
Incremental interest rate over base rate				3.25%	2.80%	2.60%	1.95%	1.45%	1.63%	3.00%	3.00%	3.00%
Contractual rate				3.49%	3.03%	2.83%	2.18%	1.68%	1.86%	3.24%	3.24%	3.23%
Issue Date				Apr. 30, 2003	Dec. 31, 2003	May 31, 2004	Dec. 31, 2004	Aug. 31, 2005	Sep. 30, 2006	Aug. 31, 2003	Aug. 31, 2003	May 31, 2004
Maturity Date				Apr. 30, 2033	Dec. 31, 2033	May 31, 2034	Mar. 31, 2035	Sep. 30, 2035	Sep. 30, 2036	Nov. 30, 2033	Nov. 30, 2033	May 31, 2034
Earliest Redemption Date				Apr. 30, 2008	Dec. 31, 2008	Jun. 30, 2009	Mar. 31, 2010	Sep. 30, 2010	Sep. 30, 2011	Aug. 31, 2008	Aug. 31, 2008	May 31, 2009