Junior Subordinated Debentures (Summary of the Company's Junior Subordinated Debentures) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Subordinated Borrowing [Line Items]
Junior subordinated debentures	$ 268,566	$ 249,493
Maturity Date	Jun. 15, 2020
Wintrust Capital Trust Three
Subordinated Borrowing [Line Items]
Common Securities	$ 774
Trust Preferred Securities	25,000
Junior subordinated debentures	$ 25,774	25,774
Rate Structure	L+3.25
Contractual Rate	3.57%
Debt instrument, issuance date	Apr. 30, 2003
Maturity Date	Apr. 30, 2033
Earliest Redemption Date	Apr. 30, 2008
Wintrust Statutory Trust Four
Subordinated Borrowing [Line Items]
Common Securities	$ 619
Trust Preferred Securities	20,000
Junior subordinated debentures	$ 20,619	20,619
Rate Structure	L+2.80
Contractual Rate	3.41%
Debt instrument, issuance date	Dec. 31, 2003
Maturity Date	Dec. 31, 2033
Earliest Redemption Date	Dec. 31, 2008
Wintrust Statutory Trust Five
Subordinated Borrowing [Line Items]
Common Securities	$ 1,238
Trust Preferred Securities	40,000
Junior subordinated debentures	$ 41,238	41,238
Rate Structure	L+2.60
Contractual Rate	3.21%
Debt instrument, issuance date	May 31, 2004
Maturity Date	May 31, 2034
Earliest Redemption Date	Jun. 30, 2009
Wintrust Capital Trust Seven
Subordinated Borrowing [Line Items]
Common Securities	$ 1,550
Trust Preferred Securities	50,000
Junior subordinated debentures	$ 51,550	51,550
Rate Structure	L+1.95
Contractual Rate	2.46%
Debt instrument, issuance date	Dec. 31, 2004
Maturity Date	Mar. 31, 2035
Earliest Redemption Date	Mar. 31, 2010
Wintrust Capital Trust Eight
Subordinated Borrowing [Line Items]
Common Securities	$ 1,238
Trust Preferred Securities	40,000
Junior subordinated debentures	$ 41,238	41,238
Rate Structure	L+1.45
Contractual Rate	2.06%
Debt instrument, issuance date	Aug. 31, 2005
Maturity Date	Sep. 30, 2035
Earliest Redemption Date	Sep. 30, 2010
Wintrust Capital Trust Nine
Subordinated Borrowing [Line Items]
Common Securities	$ 1,547
Trust Preferred Securities	50,000
Junior subordinated debentures	$ 51,547	51,547
Rate Structure	L+1.63
Contractual Rate	2.14%
Debt instrument, issuance date	Sep. 30, 2006
Maturity Date	Sep. 30, 2036
Earliest Redemption Date	Sep. 30, 2011
Northview Capital Trust One
Subordinated Borrowing [Line Items]
Common Securities	$ 186
Trust Preferred Securities	6,000
Junior subordinated debentures	$ 6,186	6,186
Rate Structure	L+3.00
Contractual Rate	3.33%
Debt instrument, issuance date	Aug. 31, 2003
Maturity Date	Nov. 30, 2033
Earliest Redemption Date	Aug. 31, 2008
Town Bankshares Capital Trust One
Subordinated Borrowing [Line Items]
Common Securities	$ 186
Trust Preferred Securities	6,000
Junior subordinated debentures	$ 6,186	6,186
Rate Structure	L+3.00
Contractual Rate	3.33%
Debt instrument, issuance date	Aug. 31, 2003
Maturity Date	Nov. 30, 2033
Earliest Redemption Date	Aug. 31, 2008
First Northwest Capital Trust One
Subordinated Borrowing [Line Items]
Common Securities	$ 155
Trust Preferred Securities	5,000
Junior subordinated debentures	$ 5,155	5,155
Rate Structure	L+3.00
Contractual Rate	3.61%
Debt instrument, issuance date	May 31, 2004
Maturity Date	May 31, 2034
Earliest Redemption Date	May 31, 2009
Suburban Illinois Capital Trust Two
Subordinated Borrowing [Line Items]
Common Securities	$ 464
Trust Preferred Securities	15,000
Junior subordinated debentures	$ 15,464	0
Rate Structure	L+1.75
Contractual Rate	2.26%
Debt instrument, issuance date	Dec. 31, 2006
Maturity Date	Dec. 31, 2036
Earliest Redemption Date	Dec. 31, 2011
Community Financial Shares Statutory Trust Two
Subordinated Borrowing [Line Items]
Common Securities	$ 109
Trust Preferred Securities	3,500
Junior subordinated debentures	$ 3,609	$ 0
Rate Structure	L+1.62
Contractual Rate	2.13%
Debt instrument, issuance date	Jun. 30, 2007
Maturity Date	Sep. 30, 2037
Earliest Redemption Date	Jun. 30, 2012
Junior Subordinated Debt
Subordinated Borrowing [Line Items]
Weighted average interest rate	2.68%
London Interbank Offered Rate (LIBOR) | Wintrust Capital Trust Three
Subordinated Borrowing [Line Items]
Debt instrument, basis spread on variable rate	3.25%
London Interbank Offered Rate (LIBOR) | Wintrust Statutory Trust Four
Subordinated Borrowing [Line Items]
Debt instrument, basis spread on variable rate	2.80%
London Interbank Offered Rate (LIBOR) | Wintrust Statutory Trust Five
Subordinated Borrowing [Line Items]
Debt instrument, basis spread on variable rate	2.60%
London Interbank Offered Rate (LIBOR) | Wintrust Capital Trust Seven
Subordinated Borrowing [Line Items]
Debt instrument, basis spread on variable rate	1.95%
London Interbank Offered Rate (LIBOR) | Wintrust Capital Trust Eight
Subordinated Borrowing [Line Items]
Debt instrument, basis spread on variable rate	1.45%
London Interbank Offered Rate (LIBOR) | Wintrust Capital Trust Nine
Subordinated Borrowing [Line Items]
Debt instrument, basis spread on variable rate	1.63%
London Interbank Offered Rate (LIBOR) | Northview Capital Trust One
Subordinated Borrowing [Line Items]
Debt instrument, basis spread on variable rate	3.00%
London Interbank Offered Rate (LIBOR) | Town Bankshares Capital Trust One
Subordinated Borrowing [Line Items]
Debt instrument, basis spread on variable rate	3.00%
London Interbank Offered Rate (LIBOR) | First Northwest Capital Trust One
Subordinated Borrowing [Line Items]
Debt instrument, basis spread on variable rate	3.00%
London Interbank Offered Rate (LIBOR) | Suburban Illinois Capital Trust Two
Subordinated Borrowing [Line Items]
Debt instrument, basis spread on variable rate	1.75%
London Interbank Offered Rate (LIBOR) | Community Financial Shares Statutory Trust Two
Subordinated Borrowing [Line Items]
Debt instrument, basis spread on variable rate	1.62%