Loans Receivable - Allowance For Credit Loss (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2020
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for expected credit losses at January 1, 2020	$ 8,719	$ 2,146
Cumulative effect adjustment resulting from changes in accounting principles	8,719	2,146
Provision for expected credit losses	(2,876)	4,054
Allowance for expected credit losses at September 30, 2020	5,843	5,843
Real estate loans
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for expected credit losses at January 1, 2020	4,318	1,502
Cumulative effect adjustment resulting from changes in accounting principles	1,759	1,759
Provision for expected credit losses	(2,559)	1,162
Allowance for expected credit losses at September 30, 2020	1,759	1,759
Commercial loans
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for expected credit losses at January 1, 2020	4,401	644
Cumulative effect adjustment resulting from changes in accounting principles	4,084	4,084
Provision for expected credit losses	(317)	2,892
Allowance for expected credit losses at September 30, 2020	$ 4,084	4,084
Cumulative effect adjustment resulting from changes in accounting principles
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for expected credit losses at January 1, 2020		(357)
Cumulative effect adjustment resulting from changes in accounting principles		(357)
Cumulative effect adjustment resulting from changes in accounting principles | Real estate loans
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for expected credit losses at January 1, 2020		(905)
Cumulative effect adjustment resulting from changes in accounting principles		(905)
Cumulative effect adjustment resulting from changes in accounting principles | Commercial loans
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for expected credit losses at January 1, 2020		548
Cumulative effect adjustment resulting from changes in accounting principles		$ 548