Goodwill and Other Intangible Assets - Narrative (Details)	12 Months Ended
	Dec. 31, 2017
Client relationships | Minimum
Finite-Lived Intangible Assets [Line Items]
Useful life of other intangible assets	5 years
Client relationships | Maximum
Finite-Lived Intangible Assets [Line Items]
Useful life of other intangible assets	20 years
Core deposits | Minimum
Finite-Lived Intangible Assets [Line Items]
Useful life of other intangible assets	16 years
Core deposits | Maximum
Finite-Lived Intangible Assets [Line Items]
Useful life of other intangible assets	22 years