Fair Value Measurements (Summary Of Changes In Level 3 Investments Measured At Fair Value On A Recurring Basis) (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Fair Value Disclosures [Abstract]
Equity securities, beginning of period		$ 178,043	$ 176,942	$ 191,203	$ 0
Purchases		1,250	25,000	7,250	195,250
Sales		(1,303)	(25,000)	(26,674)	(25,000)
Total gains included in net income		5,923	6,581	12,134	13,273
Total gains included in other comprehensive income		0	0	0	0
Transfers into level 3		0	0	0	0
Transfers out of level 3		0	0	0	0
Equity securities, end of period		183,913	183,523	183,913	183,523
Net unrealized gains included in net income relating to assets held at June 30, 2017 and 2016	[1]	$ 5,923	$ 6,581	$ 12,134	$ 13,273

[1] Included in net realized investment gains in the consolidated statements of income and comprehensive income.