Fair Value Measurement (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Unrealized losses arising during the period	$ (2,409)	$ 0	$ (5,605)	$ 0
Change in unrealized gains on junior subordinated debentures carried at fair value, net of taxes	(1,794)	0	(4,174)	0
Net gain (loss) representing the change in fair value in earnings	(6,500)	$ 136	(1,100)	$ 7,200
Accounting Standards Update 2016-01 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Unrealized losses arising during the period	(2,400)		(5,600)
Change in unrealized gains on junior subordinated debentures carried at fair value, net of taxes	$ (1,800)		$ (4,200)