Significant Accounting Policies Significant Accounting Policies (Accumulated Other Comprehensive Loss) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning of the period	$ (16)	$ (22)
Other comprehensive income before reclassifications	(12)	4
Amounts reclassified from accumulated other comprehensive income	2	2
Net current-period other comprehensive income	(10)	6
End of the period	(26)	(16)
Net Unrealized Gain/(Loss) on Investments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning of the period	1	0
Other comprehensive income before reclassifications	0	1
Amounts reclassified from accumulated other comprehensive income	0	0
Net current-period other comprehensive income	0	1
End of the period	1	1
Benefit Obligations [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning of the period	(17)	(22)
Other comprehensive income before reclassifications	(12)	3
Amounts reclassified from accumulated other comprehensive income	2	2
Net current-period other comprehensive income	(10)	5
End of the period	$ (27)	$ (17)