Debt - Convertible Debt Narrative (Details) - Convertible Debt [Member] - USD ($)	Jan. 22, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 10, 2013	Aug. 01, 2013	Jul. 29, 2013
Debt Instrument [Line Items]
Aggregate balance outstanding		$ 1,000,000,000	$ 1,000,000,000
Number of days following notice of default to deliver financial statements	60 days
2018 Convertible Notes [Member]
Debt Instrument [Line Items]
Aggregate principal amount issued				$ 287,500,000.0	$ 10,000,000.0	$ 300,000,000.0
2020 Convertible Notes [Member]
Debt Instrument [Line Items]
Aggregate principal amount issued				$ 402,500,000.0