Fair Value Measurement (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Unrealized losses arising during the period	$ (1,683)	$ 0
Change in unrealized gains on junior subordinated debentures carried at fair value, net of taxes	(1,253)	0
Net gain (loss) representing the change in fair value in earnings	(306)	$ 4,900
Accounting Standards Update 2016-01 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Unrealized losses arising during the period	(1,700)
Change in unrealized gains on junior subordinated debentures carried at fair value, net of taxes	$ (1,300)