Convertible Notes (Summary of Convertible Notes) (Detail)				1 Months Ended	3 Months Ended	12 Months Ended
	Nov. 21, 2016	Nov. 20, 2015 USD ($)	Feb. 11, 2014	Jan. 31, 2012 USD ($)	Mar. 31, 2014 USD ($)	Dec. 31, 2016 USD ($) $ / shares	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Nov. 22, 2016 USD ($) $ / shares	May 01, 2015 USD ($)	Feb. 17, 2015 USD ($)	Oct. 20, 2014 USD ($)	Sep. 30, 2014 USD ($)	Feb. 12, 2014 $ / shares	Feb. 06, 2014 USD ($)	Aug. 01, 2013 USD ($)
Debt Instrument [Line Items]
Principal amount a $5 incentive cash payment per each to convert debt						$ 1,000
Convertible Notes and Term Loans, Beginning Balance						253,828,000	$ 444,771,000
Issuance and exchange of Debt						150,000,000	100,000,000
Repayments of Debt						25,000,000	252,387,000
Payments for Repurchase of Convertible Preferred Stock						120,000,000	220,397,000	$ 56,191,000
Gains (Losses) on Extinguishment of Debt					$ 6,100,000	2,353,000	(6,450,000)	6,143,000
Non-cash discount						(3,204,000)	(607,000)
Amortization						13,472,000	15,604,000
Convertible Notes and Term Loans, Ending Balance						232,443,000	253,828,000	444,771,000
Series 2012 Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage				2.875%
Convertible Notes, Principal Balance Outstanding											$ 22,300,000	$ 22,300,000			$ 48,300,000	$ 180,000,000
Convertible Notes and Term Loans, Beginning Balance						0	22,261,000
Issuance and exchange of Debt							0
Repayments of Debt							22,337,000
Payments for Repurchase of Convertible Preferred Stock							0
Non-cash discount							0
Amortization of Debt Discount (Premium)						0	76,000	2,415,000
Amortization							76,000
Convertible Notes and Term Loans, Ending Balance						$ 0	0	22,261,000
May 2015 Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage													3.75%
Convertible notes, conversion price (in Dollars per Share) | $ / shares						$ 5.72
Convertible Notes, Principal Balance Outstanding										$ 155,100,000
Convertible Notes and Term Loans, Beginning Balance						$ 0	153,235,000
Issuance and exchange of Debt							0
Repayments of Debt							155,050,000
Payments for Repurchase of Convertible Preferred Stock							0
Non-cash discount							0
Amortization of Debt Discount (Premium)						0	1,815,000	5,182,000
Amortization							1,815,000
Convertible Notes and Term Loans, Ending Balance						0	0	153,235,000
February 2015 Notes [Member]
Debt Instrument [Line Items]
Principal amount a $5 incentive cash payment per each to convert debt				$ 1,000
Convertible Notes, Principal Balance Outstanding													$ 0
Term Loan. [Member]
Debt Instrument [Line Items]
Convertible Notes and Term Loans, Beginning Balance						24,966,000	0
Issuance and exchange of Debt							100,000,000
Repayments of Debt						25,000,000	75,000,000
Payments for Repurchase of Convertible Preferred Stock							0
Non-cash discount							(607,000)
Amortization						34,000	573,000
Convertible Notes and Term Loans, Ending Balance						0	24,966,000	0
February 2018 Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage														4.00%
Debt Instrument, Convertible, Conversion Ratio			109.1048
Convertible notes, conversion price (in Dollars per Share) | $ / shares														$ 9.17
Convertible Notes, Principal Balance Outstanding						126,447,000	246,447,000
Convertible Notes and Term Loans, Beginning Balance						228,862,000	269,275,000
Exchange of debt							0
Repayments of Debt							0
Payments for Repurchase of Convertible Preferred Stock						(120,000,000)	(53,553,000)
Gains (Losses) on Extinguishment of Debt		$ (6,500,000)
Non-cash discount							0
Amortization of Debt Discount (Premium)						9,870,000	10,160,000
Amortization						12,733,000	13,140,000
Convertible Notes and Term Loans, Ending Balance						121,595,000	228,862,000	269,275,000
December 2021 Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage									2.80%
Debt Instrument, Convertible, Conversion Ratio	262.2951
Convertible notes, conversion price (in Dollars per Share) | $ / shares									$ 3.81
Convertible Notes, Principal Balance Outstanding									$ 150,000,000
Convertible Notes and Term Loans, Beginning Balance						0	0
Issuance and exchange of Debt						150,000,000
Non-cash discount						(3,204,000)
Debt Instrument, Convertible, Beneficial Conversion Feature						(36,653,000)
Amortization of Debt Discount (Premium)						75,000
Amortization						705,000
Convertible Notes and Term Loans, Ending Balance						$ 110,848,000	$ 0	$ 0