Debt And Financing - Series B Convertible Senior Secured Notes (Details) - USD ($)			12 Months Ended
	Mar. 25, 2017	Mar. 31, 2015	Dec. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Mar. 25, 2015	Jul. 22, 2011
Debt Instrument [Line Items]
Aggregate principal amount				$ 926,100,000	$ 1,010,300,000
Senior Notes | Senior B Convertible Senior Secured Notes
Debt Instrument [Line Items]
Principal amount issued							$ 100,000,000
Interest rate							10.00%
Aggregate principal amount						$ 17,900,000
Deb instrument, convertible, conversion price (in dollars per share)						$ 18.00
Debt conversion, shares issued (in shares)	994,689
Expense related to fair value of incremental shares converted			$ 600,000
Repayments of debt		$ 300,000