Goodwill and Other Intangible Assets, Summary of Core Deposit and Other Intangibles (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Summary of core deposit intangibles and other intangibles
Amortization of other intangible assets	$ 2,168	$ 496	$ 3,693	$ 1,009
Core Deposit Intangibles
Summary of core deposit intangibles and other intangibles
Gross carrying amount	58,100		58,100		$ 4,385
Accumulated amortization	(2,421)		(2,421)		(4,385)
Net Book Value	55,679		55,679		0
Amortization of other intangible assets			2,421		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
Accumulated amortization	(20,262)		(20,262)		(18,992)
Net Book Value	$ 24,668		24,668		15,580
Additions during the period			10,359		2,162
Amortization of other intangible assets			$ 1,270		$ 1,847