Commitments and Contingent Liabilities - Summary of Commitments and Contingent Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Commitments to Grant Loans
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items]
Commitments to grant loans	$ 232,618	$ 103,570
Standby Letters of Credit
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items]
Letters of credit	174,955	141,214
Performance Letters of Credit
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items]
Performance letters of credit	17,783	21,026
Commercial Letters of Credit
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items]
Letters of credit	14,600	11,262
Commitments to Extend Credit
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items]
Commitments to extend credit	$ 4,947,709	$ 4,078,708