Junior Subordinated Debentures (Summary of the Company's Junior Subordinated Debentures) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Jan. 31, 2016	Dec. 31, 2015	Aug. 31, 2005
Subordinated Borrowing [Line Items]
Junior subordinated debentures	$ 253,566,000		$ 268,566,000
Wintrust Capital Trust Three
Subordinated Borrowing [Line Items]
Common Securities	774,000
Trust Preferred Securities	25,000,000
Junior subordinated debentures	$ 25,774,000		25,774,000
Rate Structure	L+3.25
Contractual Rate	4.13%
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	$ 619,000
Trust Preferred Securities	20,000,000
Junior subordinated debentures	$ 20,619,000		20,619,000
Rate Structure	L+2.80
Contractual Rate	3.79789%
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	$ 1,238,000
Trust Preferred Securities	40,000,000
Junior subordinated debentures	$ 41,238,000		41,238,000
Rate Structure	L+2.60
Contractual Rate	3.59817%
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	$ 1,550,000
Trust Preferred Securities	50,000,000
Junior subordinated debentures	$ 51,550,000		51,550,000
Rate Structure	L+1.95
Contractual Rate	2.91344%
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	$ 1,238,000
Trust Preferred Securities	25,000,000	$ 15,000,000.0		$ 40,000,000.0
Junior subordinated debentures	$ 26,238,000		41,238,000
Rate Structure	L+1.45
Contractual Rate	2.44789%
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	$ 1,547,000
Trust Preferred Securities	50,000,000
Junior subordinated debentures	$ 51,547,000		51,547,000
Rate Structure	L+1.63
Contractual Rate	2.59344%
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	$ 186,000
Trust Preferred Securities	6,000,000
Junior subordinated debentures	$ 6,186,000		6,186,000
Rate Structure	L+3.00
Contractual Rate	3.88594%
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	$ 186,000
Trust Preferred Securities	6,000,000
Junior subordinated debentures	$ 6,186,000		6,186,000
Rate Structure	L+3.00
Contractual Rate	3.88594%
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	$ 155,000
Trust Preferred Securities	5,000,000
Junior subordinated debentures	$ 5,155,000		5,155,000
Rate Structure	L+3.00
Contractual Rate	3.99789%
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	$ 464,000
Trust Preferred Securities	15,000,000
Junior subordinated debentures	$ 15,464,000		15,464,000
Rate Structure	L+1.75
Contractual Rate	2.71344%
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	$ 109,000
Trust Preferred Securities	3,500,000
Junior subordinated debentures	$ 3,609,000		$ 3,609,000
Rate Structure	L+1.62
Contractual Rate	2.58344%
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	3.16%
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%