Other Intangibles - Schedule of Core Deposit and Other Intangibles (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Acquired Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	$ 85,869	$ 63,940
Accumulated amortization	(59,815)	(54,721)
Total other intangibles	26,054	31,148
Core deposit intangibles acquired
Acquired Finite-Lived Intangible Assets [Line Items]
Intangibles acquired		18,164
Other intangibles
Acquired Finite-Lived Intangible Assets [Line Items]
Intangibles acquired		$ 3,765