Convertible Notes (Narrative) (Detail) $ / shares in Units, shares in Millions									1 Months Ended		3 Months Ended	12 Months Ended
	Nov. 21, 2016 USD ($)	Nov. 20, 2015 USD ($)	May 02, 2015 USD ($) shares	Feb. 18, 2015 shares	Oct. 20, 2014 USD ($) shares	Feb. 11, 2014 USD ($)	Feb. 05, 2014 USD ($) shares	May 16, 2011 USD ($)	Jan. 31, 2013 USD ($)	Jan. 31, 2012 USD ($)	Mar. 31, 2014 USD ($)	Dec. 31, 2016 USD ($) $ / shares shares	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Nov. 23, 2016 USD ($)	Nov. 22, 2016 USD ($) $ / shares	Nov. 21, 2015 USD ($)	May 01, 2015 USD ($) shares	Mar. 30, 2015 USD ($)	Feb. 17, 2015 USD ($)	Nov. 24, 2014 USD ($)	Oct. 28, 2014	Sep. 30, 2014 USD ($)	Feb. 12, 2014 USD ($) $ / shares	Feb. 07, 2014 USD ($)	Feb. 06, 2014 USD ($) $ / shares	Oct. 28, 2013 USD ($)	Aug. 01, 2013 USD ($)	Feb. 29, 2012 USD ($)
Debt Instrument [Line Items]
Principal amount a $5 incentive cash payment per each to convert debt												$ 1,000
Adjustments to additional paid in capital, equity component of convertible debt														$ 102,134,000
Convertible note rate conversion trading days (in days)												0
Convertible Notes rate conversion consecutive trading days (in days)												$ 30
Debt Conversion, Original Debt, Amount					$ 26,000,000
Minimum conversion price percent for note conversion (in Percent)												130.00%
Convertible Notes rate conversion business day period (in days)												$ 5
Share Price | $ / shares																										$ 7.97
Net proceeds from the issuance of convertible notes												150,000,000	$ 0	300,000,000
Interest Paid												11,410,000	16,987,000	18,439,000
Purchased call options cost												(14,400,000)	0	(30,951,000)
Proceeds from issuance of warrants												$ 0	0	11,427,000
Dividends Payable, Amount Per Share | $ / shares												$ 0.15
Deferred Income Tax Expense (Benefit)												$ (9,429,000)	17,067,000	(30,659,000)
Gains (loss) on extinguishment of debt											$ (6,100,000)	(2,353,000)	6,450,000	(6,143,000)
Debt instrument, increase, additional borrowings												$ 150,000,000	100,000,000
February 2018 Note Warrant [Member]
Debt Instrument [Line Items]
Convertible notes, conversion price (in Dollars per Share) | $ / shares												$ 10.3610
Proceeds from issuance of warrants							$ 11,400,000
December 2021 Notes [Member]
Debt Instrument [Line Items]
Convertible Debt		$ 150,000,000										$ 110,848,000				$ 150,000,000
Unamortized discount of liability component												$ (39,152,000)				$ (4,300,000)
Debt Instrument, Interest Rate, Stated Percentage																2.80%
Debt discount recorded to additional paid in capital																$ 23,800,000
Debt discount recorded to deferred tax liability																$ 12,800,000
Debt Instrument, Interest Rate, Effective Percentage																3.40%
Convertible notes, conversion price (in Dollars per Share) | $ / shares																$ 3.81
Estimated market interest rate for similar nonconvertible instrument																9.50%
Debt instrument, convertible, remaining amortization period (in Duration)												4 years 11 months 6 days
Net proceeds from the issuance of convertible notes	$ 145,700,000
Debt Instrument, Face Amount																$ 150,000,000
Conversion Rate per $1,000 Principal Amount (in Ratio)	262.2951
Proceeds from issuance of warrants							$ 14,400,000
Debt instrument, increase, additional borrowings												$ 150,000,000
February 2018 Note Purchase Call Option [Member]
Debt Instrument [Line Items]
Number of hedge counterparties (in Counterparties)																							2
Purchased call options cost						$ 31,000,000
Deferred taxes included in purchased call options cost						10,800,000
Number of shares of common stock covered by the purchased call options purchased (in Shares) | shares												13.8
Series 2012 Notes [Member]
Debt Instrument [Line Items]
Convertible Debt																				$ 22,300,000	$ 26,000,000				$ 131,700,000	$ 131,700,000			$ 10,000,000
Total consideration given for convertible note exchange																										191,800,000
Induced conversion of convertible debt expense										$ 845,000
Deferred issue costs, incentive payment allocated										765,000
Adjustments to additional paid in capital, equity component of convertible debt										52,000
Noted obligation allocated to deferred tax assets										$ 28,000
Unamortized discount of liability component					(100,000)																			$ (2,100,000)
Debt Instrument, Interest Rate, Stated Percentage										2.875%
Debt Instrument, Face Amount					$ 22,300,000															$ 22,300,000						48,300,000		$ 180,000,000
Debt conversion, shares issued (in Shares) | shares				1.3	1.8		20.3
Debt Conversion, Converted Instrument, Amount							$ 157,600,000
Cash paid to exchange convertible note					$ 26,200,000																					34,200,000
Inducement fee																										2,500,000
Interest Payable																										1,800,000
Deferred Income Tax Expense (Benefit)							$ 29,900,000
Debt discount, derecognition on exchange																										5,800,000
Debt Exchange cost other																										$ 300,000
Debt instrument, increase, additional borrowings													0
May 2015 Notes [Member]
Debt Instrument [Line Items]
Convertible Debt								$ 155,300,000
Debt Instrument, Interest Rate, Stated Percentage																							3.75%
Minimum conversion price percent for note conversion (in Percent)												130.00%
Maximum percent of common stock closing price and conversion rate to convert note (in Percent)												98.00%
Convertible notes, conversion price (in Dollars per Share) | $ / shares												$ 5.72
Net proceeds from the issuance of convertible notes								$ 149,700,000
Convertible notes repurchase price as a percentage of principal (in Percent)								100.00%
Debt Instrument, Face Amount																		$ 155,100,000
Debt conversion, shares issued (in Shares) | shares			5.2
Debt instrument, increase, additional borrowings													0
Purchased Call Options [Member]
Debt Instrument [Line Items]
Convertible notes, conversion price (in Dollars per Share) | $ / shares												4.88
Purchased call options cost			$ 20,800,000
Warrants [Member]
Debt Instrument [Line Items]
Convertible notes, conversion price (in Dollars per Share) | $ / shares												$ 6.73
Number of shares of common stock covered by the purchased call options purchased (in Shares) | shares																		27.5
Proceeds from issuance of warrants									$ 10,900,000
February 2015 Notes [Member]
Debt Instrument [Line Items]
Convertible Debt										$ 169,000,000																		$ 1,000,000
Incentive fee per each $1,000 principal amount tendered to convert debt										5.00
Principal amount a $5 incentive cash payment per each to convert debt										$ 1,000
Debt Instrument, Face Amount																							$ 0
Term Loan. [Member]
Debt Instrument [Line Items]
Debt instrument, increase, additional borrowings													100,000,000
Short-term Debt																											$ 75,000,000
Term Loan. [Member] | Base Rate [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage																						2.22%					1.00%
February 2018 Notes [Member]
Debt Instrument [Line Items]
Convertible Debt		246,400,000										$ 121,595,000	228,862,000			126,400,000								300,000,000
Adjustments to additional paid in capital, equity component of convertible debt												25,465,000		$ 18,689,000
Unamortized discount of liability component		(3,100,000)										$ (4,852,000)	(17,585,000)		$ (4,600,000)	(4,300,000)	$ (14,100,000)							$ (29,700,000)
Deferred issuance costs		900,000													$ 1,400,000	1,300,000	$ 4,100,000
Purchase call option unwind		270,000
Warrant unwind		170,000
Fees and Commissions, Transfer Agent		100,000
Debt Instrument, Interest Rate, Stated Percentage																								4.00%
Debt discount recorded to additional paid in capital																								$ 19,300,000
Debt discount recorded to deferred tax liability																								$ 10,400,000
Debt Instrument, Interest Rate, Effective Percentage																								6.90%
Convertible notes, conversion price (in Dollars per Share) | $ / shares																								$ 9.17
Estimated market interest rate for similar nonconvertible instrument																								7.00%
Debt instrument, convertible, remaining amortization period (in Duration)												1 year 1 month 2 days
Net proceeds from the issuance of convertible notes						$ 290,200,000
Debt Instrument, Repurchase Amount		53,600,000														120,000,000
Debt instrument, repurchase amount paid		43,700,000														$ 121,500,000
Interest Paid	$ 1,500,000
Debt Instrument, Face Amount												$ 126,447,000	$ 246,447,000
Conversion Rate per $1,000 Principal Amount (in Ratio)						109.1048
Gains (loss) on extinguishment of debt		$ 6,500,000
March 2015 Term Loan [Member]
Debt Instrument [Line Items]
Short-term Debt																			$ 100,000,000
March 2015 Term Loan [Member] | Base Rate [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage												2.17%							0.75%