Loans Receivable - Allowance For Credit Loss (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for expected credit losses at December 31, 2020	$ 5,437	$ 2,146
Cumulative effect adjustment resulting from changes in accounting principles	5,437	3,928
Provision for expected credit losses	(1,239)	2,139
Allowance for expected credit losses at March 31, 2021	4,198	3,928
Real estate loans
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for expected credit losses at December 31, 2020	1,683	1,502
Cumulative effect adjustment resulting from changes in accounting principles	1,608	1,435
Provision for expected credit losses	(75)	838
Allowance for expected credit losses at March 31, 2021	1,608	1,435
Commercial loans
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for expected credit losses at December 31, 2020	3,754	644
Cumulative effect adjustment resulting from changes in accounting principles	2,590	2,493
Provision for expected credit losses	(1,164)	1,301
Allowance for expected credit losses at March 31, 2021	$ 2,590	2,493
Cumulative effect adjustment resulting from changes in accounting principles
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for expected credit losses at December 31, 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 December 31, 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 December 31, 2020		548
Cumulative effect adjustment resulting from changes in accounting principles		$ 548