Intangible Assets and Goodwill - Summary of Goodwill by Business Segment (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Goodwill [Line Items]
Balance at beginning of period	$ 54,042	$ 54,042
Balance at end of period	54,042	54,042
Metropolitan Banks [Member]
Goodwill [Line Items]
Balance at beginning of period	8,078	8,078
Balance at end of period	8,078	8,078
Community Banks [Member]
Goodwill [Line Items]
Balance at beginning of period	40,050	40,050
Balance at end of period	40,050	40,050
Other Financial Services [Member]
Goodwill [Line Items]
Balance at beginning of period	5,464	5,464
Balance at end of period	5,464	5,464
Executive, Operations & Support [Member]
Goodwill [Line Items]
Balance at beginning of period	450	450
Balance at end of period	$ 450	$ 450