Other Intangible Assets - Intangible Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Carrying amount, accumulated amortization and amortization expense of core deposit intangible assets
Total intangible assets	$ 32,833	$ 34,271
Core deposit intangible assets
Carrying amount, accumulated amortization and amortization expense of core deposit intangible assets
Gross original amount	56,456	59,143
Accumulated amortization	23,623	24,884
Total intangible assets	32,833	34,259
Non-compete intangible assets
Carrying amount, accumulated amortization and amortization expense of core deposit intangible assets
Total intangible assets	$ 0	$ 12