Subsequent event (Details) - Subsequent event - Share Repurchase Program, May 2017 $ in Billions	1 Months Ended
May 31, 2017 USD ($)
Subsequent event
Amount authorized per the share repurchase program	$ 6.0
Period in force	2 years

Detail information of subsequent event by type. User is expected to use existing line items from elsewhere in the taxonomy as the primary line items for this disclosure, which is further associated with dimension and member elements pertaining to a subsequent event.

No definition available.

Name:	us-gaap_SubsequentEventLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration