Fair Value Measurements (Details) - USD ($) $ in Thousands		Dec. 31, 2017	Dec. 31, 2016
Fair value measurements
Fair value carrying amount		$ 13,123	$ 15,849
Mortgages held for sale reported at fair value
Fair value measurements
Fair value carrying amount		13,123	15,849
Aggregate unpaid principal		12,967	15,809
Excess of fair value carrying amount over (under) unpaid principal	[1]	$ 156	$ 40

[1] The excess of fair value carrying amount over (under) unpaid principal is included in mortgage banking income and includes changes in fair value at and subsequent to funding and gains and losses on the related loan commitment prior to funding.