Fair Value - Measurement Basis, Nonrecurring (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Total gains (losses) on assets measured at estimated fair values on a nonrecurring basis
Notes Payable	$ 1,292,736		$ 1,292,291
Nonrecurring basis
Financial statement items measured at fair value on a nonrecurring basis
Real estate acquired in settlement of loans	719		2,150
Total gains (losses) on assets measured at estimated fair values on a nonrecurring basis
Real estate acquired in settlement of loans	21	$ 27
Nonrecurring basis | Level 3
Financial statement items measured at fair value on a nonrecurring basis
Real estate acquired in settlement of loans	719		2,150
Fair Values
Total gains (losses) on assets measured at estimated fair values on a nonrecurring basis
Notes Payable	$ 1,300,000		$ 1,300,000