Statements of Cash Flows (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Statement of cash flows specific transaction amounts [Abstract]
Income taxes paid	$ 11,629	$ 1,423
Interest expense paid on deposits and borrowings	46,506	28,266
Noncash transfers from loans to other real estate	$ 10,368	7,006
Transfer of long-term FHLB advances to short-term		250,038
Assets acquired in business combination		196,265
Liabilities acquired in business combination		$ 184,949