Fair value measurements Fair Value Measurement- Nonrecurring Basis (Details) - Indefinite-lived Intangible Assets [Member] - Fair Value, Inputs, Level 3 [Member]	12 Months Ended
Dec. 31, 2016 USD ($)
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis
Assets, Fair Value Disclosure, Nonrecurring	$ 0
Assets, Fair Value Adjustment	$ 432,000,000

This element represents the aggregate of the assets reported on the balance sheet at period end measured at fair value on a nonrecurring basis by the entity. This element is intended to be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements.

No definition available.

Name:	us-gaap_AssetsFairValueDisclosureNonrecurring
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant