Fair Value of Assets and Liabilities (Narrative) (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Transfers Between Level 1 and Level 2	$ 0	$ 0	$ 0	$ 0
Accounting Standards Update 2015-07 | Other long-term investments | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	1,000,000		1,000,000		$ 1,000,000
Accounting Standards Update 2015-07 | Separate Account Assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	$ 493,000,000		$ 493,000,000		$ 383,000,000