Corporate Debt - Additional Information (Details) - USD ($)		5 Months Ended	12 Months Ended
	Aug. 04, 2016	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 10, 2013	Oct. 31, 2012
Debt Instrument [Line Items]
Effective interest rate on corporate debt		6.64%	6.64%	6.56%
Loss on extinguishment of debt			$ (14,662,000)	$ (4,660,000)	$ 0
2013 Term Loan [Member]
Debt Instrument [Line Items]
Face amount of debt		$ 1,500,000,000.0	$ 1,500,000,000.0
Variable Interest Rate Basis			Libor
Interest rate spread			3.75%
Corporate debt		1,394,658,000	$ 1,394,658,000	1,396,884,000
Early repayment of long-term debt			50,000,000
Loss on extinguishment of debt			1,000,000
Unpaid principal balance of repurchased debt				7,200,000
Amount paid for repurchased debt				6,300,000
Gain on extinguishment			$ (900,000)
Payment Terms			1.00% per annum beginning 1st quarter 2014; remainder at final maturity
Maturity Date			Dec. 18, 2020
Senior Notes [Member]
Debt Instrument [Line Items]
Face amount of debt						$ 575,000,000.0
Corporate debt		$ 529,738,000	$ 529,738,000	528,337,000
Unpaid principal balance of repurchased debt				36,300,000
Amount paid for repurchased debt				30,000,000
Gain on extinguishment				5,700,000
Payment Terms			The Senior Notes pay interest semi-annually on June 15 and December 15, commencing on June 15, 2014
Fixed Interest Rate		7.875%	7.875%
Maturity Date			Dec. 15, 2021
Carrying value of repurchased debt				$ 35,700,000
Convertible Notes [Member]
Debt Instrument [Line Items]
Effective interest rate on corporate debt		11.00%	11.00%	10.60%	10.60%
Face amount of debt							$ 290,000,000
Corporate debt		$ 204,604,000	$ 204,604,000	$ 231,723,000
Unpaid principal balance of repurchased debt		47,500,000	47,500,000
Amount paid for repurchased debt		$ 24,800,000	24,800,000
Gain on extinguishment			$ 14,500,000
Payment Terms			The Convertible Notes pay interest semi-annually on May 1 and November 1, commencing on May 1, 2013
Fixed Interest Rate		4.50%	4.50%
Maturity Date			Nov. 01, 2019
Carrying value of repurchased debt		$ 39,300,000	$ 39,300,000
Conversion Ratio			17.0068
Debt Principal Amount For Conversion Ratio			$ 1,000
Conversion Price		$ 58.80	$ 58.80
Premium to the public offering			40.00%
Public offering price per share							$ 42.00
Interest Expense			$ 24,500,000	24,600,000	$ 23,400,000
Amortization of discount and debt issuance costs			11,200,000	10,800,000	$ 9,800,000
Unamortized discount		$ 34,700,000	$ 34,700,000	$ 53,500,000
Remaining Discount Amortization Period			2 years 9 months 18 days
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Aggregate borrowing capacity	$ 125,000,000.0	$ 100,000,000.0	$ 100,000,000.0
Variable Interest Rate Basis	LIBOR	LIBOR	Libor
Interest rate spread	3.75%	4.50%	4.50%
Percentage of revolving commitments utilized, testing threshold		20.00%
Corporate debt		$ 7,800,000	$ 7,800,000
Remaining availability after reductions for issued letters of credit		$ 12,200,000	$ 12,200,000
Commitment fee on unused portion of Revolver			0.50%
Payment Terms			Bullet payment at maturity
Maturity Date			Dec. 19, 2018