Goodwill and Other Intangible Assets, Summary of Core Deposit and Other Intangibles (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Summary of core deposit intangibles and other intangibles
Amortization of other intangible assets	$ 2,226	$ 1,525
Core Deposit Intangibles
Summary of core deposit intangibles and other intangibles
Gross carrying amount	58,100		$ 58,100
Accumulated amortization	(6,778)		(5,326)
Net Book Value	51,322		52,774
Amortization of other intangible assets	1,453		5,326
Additions to Core Deposits
Summary of core deposit intangibles and other intangibles
Additions during the period	0		58,100
Other Intangibles
Summary of core deposit intangibles and other intangibles
Gross carrying amount	44,887		44,931
Reductions due to sale	0		(43)
Accumulated amortization	(22,599)		(21,825)
Net Book Value	22,288		23,062
Additions during the period	0		10,359
Amortization of other intangible assets	$ 774		$ 2,833