Core Deposit Intangibles - Intangible Assets (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Carrying amount, accumulated amortization and amortization expense of core deposit intangible assets
Total intangible assets	$ 25,835	$ 28,556
Core deposit intangible assets
Carrying amount, accumulated amortization and amortization expense of core deposit intangible assets
Gross original amount	56,456	56,456
Accumulated amortization	30,621	27,900
Total intangible assets	$ 25,835	$ 28,556