Regulatory Matters (Schedule Of Adjusted Total Risk Based Capital Ratios) (Detail) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015
Beverly Bank
Entity Information [Line Items]
Subordinated debt excluded from Tier Two Capital	$ 13,000	$ 13,000	$ 11,000	$ 11,000	$ 1,000
Total Capital (to Risk Weighted Assets)	9.70%	9.60%	10.10%	10.20%	11.00%
Schaumburg Bank
Entity Information [Line Items]
Subordinated debt excluded from Tier Two Capital	$ 8,500	$ 8,500	$ 3,500	$ 3,500	$ 3,500
Total Capital (to Risk Weighted Assets)	10.20%	10.30%	10.70%	10.80%	10.70%
Barrington Bank
Entity Information [Line Items]
Subordinated debt excluded from Tier Two Capital	$ 5,000	$ 0	$ 0	$ 0	$ 0
Total Capital (to Risk Weighted Assets)	11.40%	11.30%	11.60%	11.40%	11.10%
Old Plank Trail Bank
Entity Information [Line Items]
Subordinated debt excluded from Tier Two Capital	$ 4,000	$ 0	$ 0	$ 0	$ 0
Total Capital (to Risk Weighted Assets)	10.80%	11.30%	11.80%	11.60%	11.90%
Lake Forest Bank
Entity Information [Line Items]
Subordinated debt excluded from Tier Two Capital	$ 10,000	$ 10,000	$ 10,000	$ 14,000	$ 14,000
Total Capital (to Risk Weighted Assets)	11.80%	10.90%	11.00%	10.80%	10.80%
Libertyville Bank
Entity Information [Line Items]
Subordinated debt excluded from Tier Two Capital	$ 0	$ 0	$ 0	$ 2,500	$ 2,500
Total Capital (to Risk Weighted Assets)	11.70%	11.50%	11.20%	11.30%	11.00%
Northbrook Bank
Entity Information [Line Items]
Subordinated debt excluded from Tier Two Capital	$ 12,500	$ 6,500	$ 6,500	$ 7,500	$ 7,500
Total Capital (to Risk Weighted Assets)	10.30%	10.50%	10.70%	10.60%	10.60%
St. Charles Bank
Entity Information [Line Items]
Subordinated debt excluded from Tier Two Capital	$ 2,500	$ 2,500	$ 2,500	$ 2,000	$ 2,000
Total Capital (to Risk Weighted Assets)	11.10%	10.90%	10.90%	10.80%	10.80%
State Bank Of Lakes
Entity Information [Line Items]
Subordinated debt excluded from Tier Two Capital	$ 3,500	$ 3,500	$ 3,500	$ 3,500	$ 2,500
Total Capital (to Risk Weighted Assets)	11.00%	10.60%	10.90%	10.90%	10.90%
Village Bank
Entity Information [Line Items]
Subordinated debt excluded from Tier Two Capital	$ 2,500	$ 2,500	$ 2,500	$ 7,000	$ 7,000
Total Capital (to Risk Weighted Assets)	11.00%	11.00%	10.90%	11.00%	10.50%
Wheaton Bank
Entity Information [Line Items]
Subordinated debt excluded from Tier Two Capital	$ 15,500	$ 13,500	$ 13,500	$ 6,000	$ 0
Total Capital (to Risk Weighted Assets)	10.20%	10.10%	10.40%	10.60%	11.50%
Wintrust Bank
Entity Information [Line Items]
Subordinated debt excluded from Tier Two Capital	$ 17,000	$ 13,000	$ 13,000	$ 13,000	$ 6,000
Total Capital (to Risk Weighted Assets)	10.90%	10.90%	10.90%	11.10%	11.20%