Fair Values of Financial Instruments (Reconciliation of Beginning and Ending Balances of Level 3 Liabilities) (Details) (Fair Value, Measurements, Recurring [Member], USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Fair Value, Measurements, Recurring [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ 4,406,163	$ 3,337,556
Premiums less benefits	1,700,827	1,485,109
Change in fair value, net	(532,337)	(416,502)
Ending balance	$ 5,574,653	$ 4,406,163