Fair Value Measurement (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Fair Value Disclosures [Abstract]
Unrealized (losses) gains arising during the period	$ (37,450)	$ 17,240	$ 41,412	$ 23,804
Changes in unrealized gains and losses on junior subordinated debentures carried at fair value, net of taxes	(27,818)	12,781	30,761	17,701
Net increase (decrease) in fair value	$ 6,200	$ 4,900	$ 14,300	$ 7,700