Income Taxes - Summary of Changes In Tax Provisions (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Movement In Deferred Tax Asset [Roll Forward]
Balance at December 31, 2014	$ 0	$ 902,300
Valuation allowance	$ 0	161,158	$ 88,833
Balance at December 31, 2015		0	$ 902,300
Deferred Tax Asset, Changes In Current Period
Movement In Deferred Tax Asset [Roll Forward]
Valuation allowance		(154,800)
Deferred Tax Asset, Changes In Current Period | Other Comprehensive Income (Loss)
Movement In Deferred Tax Asset [Roll Forward]
Valuation allowance		6,300
Deferred Tax Asset, Changes In Current Period | Income Tax Expense (Benefit)
Movement In Deferred Tax Asset [Roll Forward]
Valuation allowance		(161,100)
Deferred Tax Asset, Changes In Future Periods
Movement In Deferred Tax Asset [Roll Forward]
Valuation allowance		(747,500)
Deferred Tax Asset, Changes In Future Periods | Other Comprehensive Income (Loss)
Movement In Deferred Tax Asset [Roll Forward]
Valuation allowance		(60,800)
Deferred Tax Asset, Changes In Future Periods | Income Tax Expense (Benefit)
Movement In Deferred Tax Asset [Roll Forward]
Valuation allowance		$ (686,700)