Fair Value of Assets and Liabilities - Narrative (Details) - Senior Notes	Jun. 30, 2017	Dec. 31, 2016
5.875% Senior Notes, due 2024
Debt Instrument [Line Items]
Interest rate	5.875%	5.875%
5.125% Senior Notes, due 2023
Debt Instrument [Line Items]
Interest rate	5.125%	5.125%
5.875% Senior Notes, due 2022
Debt Instrument [Line Items]
Interest rate	5.875%	5.875%
6.00% Senior Notes
Debt Instrument [Line Items]
Interest rate	6.00%	6.00%

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

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