Summary of Significant Accounting Policies and Nature of Operations (Policies)	6 Months Ended
	Jun. 30, 2021
Accounting Policies [Abstract]
Basis of Presentation	The unaudited consolidated financial statements of MUAH, its subsidiaries, and its consolidated variable interest entities have been prepared in accordance with accounting principles generally accepted in the United States of America (GAAP) for interim financial reporting and the instructions to Form 10-Q and Rule 10-01 of Regulation S-X of the Rules and Regulations of the SEC. However, they do not include all of the disclosures necessary for annual financial statements. In the opinion of management, all adjustments, consisting of normal recurring accruals, considered necessary for a fair presentation have been included.
Use of Estimates	The preparation of financial statements in conformity with GAAP also requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenue and expense during the reporting period. Although such estimates contemplate current conditions and management’s expectations of how they may change in the future, it is reasonably possible that actual results could differ significantly from those estimates. This could materially affect the Company’s results of operations and financial condition in the near term. Critical estimates made by management in the preparation of the Company’s financial statements include, but are not limited to, the allowance for credit losses (Note 3 "Loans and Allowance for Loan Losses"), goodwill impairment, income taxes, and transfer pricing.