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, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Fair Value Disclosures [Abstract]
Equity securities, beginning of period		$ 176,942	$ 0	$ 0	$ 0
Purchases		25,000	0	195,250	0
Sales		(25,000)	0	(25,000)	0
Total gains included in net income		6,581	0	13,273	0
Total gains included in other comprehensive income (loss)		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		183,523	0	183,523	0
Net unrealized gains included in net income relating to assets held at June 30, 2016 and 2015	[1]	$ 6,581	$ 0	$ 13,273	$ 0

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