Goodwill and Other Intangible Assets, Summary of Core Deposit and Other Intangibles (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Summary of core deposit intangibles and other intangibles
Amortization of other intangible assets	$ 2,233	$ 450	$ 5,926	$ 1,459
Core Deposit Intangibles
Summary of core deposit intangibles and other intangibles
Gross carrying amount	58,100		58,100		$ 4,385
Accumulated amortization	(3,873)		(3,873)		(4,385)
Net Book Value	54,227		54,227		0
Amortization of other intangible assets			3,873		112
Adjustments to Core Deposits [Member]
Summary of core deposit intangibles and other intangibles
Additions during the period			58,100		0
Other Intangible Assets
Summary of core deposit intangibles and other intangibles
Gross carrying amount	44,931		44,931		34,572
Finite-Lived Intangible Assets, Period Increase (Decrease)			(43)		0
Accumulated amortization	(21,045)		(21,045)		(18,992)
Net Book Value	$ 23,843		23,843		15,580
Additions during the period			10,359		2,162
Amortization of other intangible assets			$ 2,053		$ 1,847