CONSOLIDATED STATEMENTS OF FINANCIAL CONDITION (Parenthetical) - $ / shares	Jun. 30, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Preferred stock; no par value (in dollars per share)	$ 0	$ 0
Preferred stock, Authorized shares	10,000,000	10,000,000
Preferred stock, issued shares	0	0
Preferred stock, outstanding shares	0	0
Common stock; no par value (in dollars per share)	$ 0	$ 0
Common stock, Authorized shares	40,000,000	40,000,000
Common stock, issued shares	28,205,674	28,205,674
Cost of common stock in treasury, shares	2,240,597	2,268,910