Commitments and Contingencies - Summary of Financial Instruments with Off-Balance Sheet Credit Risk (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items]
Financial instruments with off-balance sheet credit loss	$ 978,453	$ 602,426
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	951,679	579,879
Letter of Credit
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items]
Financial instruments with off-balance sheet credit loss	$ 26,774	$ 22,547