Fair Value - Carrying Value of Mortgage Servicing Rights (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017
Servicing Asset at Fair Value, Amount [Roll Forward]
Beginning balance		$ 5,894	$ 6,120
New MSRs		176	156
Total losses (gains) included in earnings:
Changes in valuation inputs and assumptions	[1]	560	172
Other changes in fair value	[1],[2]	(162)	(203)
Ending balance		6,468	6,245
Contractual servicing fees earned	[1]	$ 378	$ 395

[1] Included in mortgage banking income in the Condensed Consolidated Statements of Income and related to assets held as of March 31, 2018 and 2017.

[2] Primarily represents changes in expected future cash flows due to payoffs and paydowns.