Goodwill and Other Intangible Assets, Summary of Core Deposit and Other Intangibles (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Summary of core deposit intangibles and other intangibles
Amortization of other intangible assets	$ 1,525	$ 513
Core Deposit Intangibles
Summary of core deposit intangibles and other intangibles
Gross carrying amount	58,100		$ 4,385
Accumulated amortization	(968)		(4,385)
Total Estimated Amortization Expense	57,132		0
Amortization of other intangible assets	968	112
Adjustments to Core Deposits [Member]
Summary of core deposit intangibles and other intangibles
Total Estimated Amortization Expense	58,100		0
Other Intangible Assets
Summary of core deposit intangibles and other intangibles
Gross carrying amount	42,131		34,572
Accumulated amortization	(19,549)		(18,992)
Total Estimated Amortization Expense	22,582		$ 15,580
Additions during the period	7,559	2,162
Amortization of other intangible assets	$ 557	$ 1,847