CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Statement Of Financial Position [Abstract]
Investments in partnerships, used as collateral	$ 349,362	$ 296,855
Loans to a related party	$ 0	$ 53,600
Preferred shares, no par value	$ 0	$ 0
Preferred shares, shares authorized	5,000,000	5,000,000
Preferred shares, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0	$ 0
Common stock, authorized	50,000,000	50,000,000
Common shares, shares issued (in shares)	5,702,423	5,701,946
Common shares, shares outstanding (in shares)	5,702,423	5,701,946
Common shares, non-employee directors' and employee deferred shares (in shares)	104,916	103,069