Fair Value Measurement - Nonrecurring (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Balances of the assets and liabilities measured at fair value on a nonrecurring basis
Loss	$ 600	$ 900	$ 600	$ 600	$ 800	$ 1,275	$ 900	$ 600	$ 2,700	$ 3,575	$ 4,175
Nonrecurring
Balances of the assets and liabilities measured at fair value on a nonrecurring basis
Loss									206	396	109
Nonrecurring | Impaired Loans
Balances of the assets and liabilities measured at fair value on a nonrecurring basis
Loss									206	396	109
Level 2 | Nonrecurring
Balances of the assets and liabilities measured at fair value on a nonrecurring basis
Assets measured at fair value	75				426				75	426	464
Level 2 | Nonrecurring | Impaired Loans
Balances of the assets and liabilities measured at fair value on a nonrecurring basis
Assets measured at fair value	$ 75				$ 426				$ 75	$ 426	$ 464