Condensed Financial Information of Registrant Condensed Financial Information of Registrant - Guarantee (Details) - USD ($)	12 Months Ended
Dec. 31, 2015	Aug. 31, 2011	Aug. 31, 2010
Condensed Financial Information of Parent Company Only Disclosure [Abstract]
Maximum borrowing capacity under credit agreement	$ 800,000,000	$ 125,000,000	$ 100,000,000
Voting equity guarantee on indebtedness, percentage	65.00%
Non-voting guarantee on indebtedness, percentage	100.00%

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

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 210.5-02.19(b),22(b))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 02
-Paragraph 19, 22
-Article 5

Name:	us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant