Debt (details) - Payment - USD ($) $ in Millions		6 Months Ended
Jun. 20, 2016	Jun. 30, 2016
Debt Instrument
Debt, principal amount repaid		$ 400
6.25% Senior notes due June 20, 2016 [Member]
Debt Instrument
Debt, principal amount repaid	$ 400
Interest rate (percent)	6.25%

Contractual interest rate for funds borrowed, under the debt agreement.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant