Fair Value Measurements - Recurring Reconciliation (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Reconciliation of items measured at fair value on a recurring basis that used significant unobservable inputs (Level 3)
Balance at the beginning of the period	$ 18	$ 15	$ 12	$ 15
Total gains or losses included in earnings	0	0	0	0
Total gains or losses included in other comprehensive income	0		0	0
Purchases and issuances	0	0	6	0
Sales and settlements	0	0	0	0
Transfers in and/or out of Level 3	0	0	0	0
Balance at the end of the period	$ 18	$ 15	$ 18	$ 15