Junior Subordinated Debentures (Narrative) (Details) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2013	Dec. 31, 2015 USD ($) Rate	Dec. 31, 2013	Dec. 31, 2014 USD ($)
Subordinated Borrowing [Line Items]
Percentage ownership interest in subsidiary trusts		100.00%
Number of unconsolidated subsidiary trusts		11
Common securities, approximate percentage of junior subordinated debentures		3.00%
Trust preferred securities, approximate percentage of junior subordinated debentures		97.00%
Junior subordinated debentures		$ 268,566		$ 249,493
Consecutive quarters of deferred payment		20
Wintrust Capital Trust Nine
Subordinated Borrowing [Line Items]
Junior subordinated debentures		$ 51,547		$ 51,547
Junior Subordinated Debt
Subordinated Borrowing [Line Items]
Debt, weighted average interest rate | Rate		2.68%
Debt, hedge adjusted weighted average interest rate | Rate		3.34%
Tier 1 Capital to Risk Weighted Assets, Amount		$ 65,100
Tier Two Risk Based Capital		195,400
Cash flow hedge of junior subordinated debentures | Designated as hedging instrument | Cash flow hedging | Interest rate cap
Subordinated Borrowing [Line Items]
Interest rate swaps to hedge variable cash flows		$ 90,000
Number of derivative contracts		2
Cash flow hedge of junior subordinated debentures | Designated as hedging instrument | Cash flow hedging | Interest rate swaps and caps
Subordinated Borrowing [Line Items]
Interest rate swaps to hedge variable cash flows		$ 225,000
Cash flow hedge of junior subordinated debentures | Designated as hedging instrument | Cash flow hedging | Interest rate swap
Subordinated Borrowing [Line Items]
Number of derivative contracts			2
Derivative, maturity date	Sep. 30, 2013