Commitments and Contingencies - Summary of Financial Instruments with Off-Balance Sheet Credit Risk (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items]
Financial instruments with off-balance sheet credit loss	$ 981,485	$ 1,000,158
Commitments to Extend Credit, Excluding Interest Rate Lock Commitments
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items]
Financial instruments with off-balance sheet credit loss	959,271	977,276
Letter of Credit
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items]
Financial instruments with off-balance sheet credit loss	$ 22,214	$ 22,882