Fair Value Measurements Fair Value Measurements - Non-Designated Derivative Instruments Activities Disclosure (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Net Periodic Cash Settlements and Accrued Interest	[1]	$ 0	$ 45	$ 0	$ 133
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net		$ 0	$ 3	$ 7	$ 12

[1] The derivative settlements under the terms of the interest rate swap agreements were recognized as interest expense and were paid monthly or quarterly prior to their expiration in January 2015.