Convertible Notes (Narrative) (Detail) $ / shares in Units, shares in Millions								1 Months Ended		3 Months Ended	12 Months Ended
	Nov. 20, 2015 USD ($)	May. 02, 2015 shares	Feb. 18, 2015 shares	Oct. 20, 2014 USD ($) shares	Feb. 11, 2014 USD ($)	Feb. 05, 2014 USD ($) shares	May. 16, 2011 USD ($) shares	Jan. 31, 2013 USD ($)	Jan. 31, 2012 USD ($)	Mar. 31, 2014 USD ($)	Dec. 31, 2015 USD ($) $ / shares shares	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Nov. 21, 2015 USD ($)	May. 01, 2015 USD ($)	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
Convertible Notes rate conversion business day period (in days)											5
Share Price | $ / shares																							$ 7.97
Net proceeds from the issuance of convertible notes											0	300,000,000	$ 0
Purchased call options cost											0	(30,951,000)	0
Proceeds from issuance of warrants											$ 0	11,427,000	0
Dividends Payable, Amount Per Share | $ / shares											$ 0.15
Deferred Income Tax Expense (Benefit)											$ 17,067,000	(30,659,000)	(999,000)
Gains (Losses) on Extinguishment of Debt										$ (6,100,000)	6,450,000	(6,143,000)	$ 0
Debt instrument, increase, additional borrowings											$ 100,000,000	147,016,000
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
February 2018 Note Purchase Call Option [Member]
Debt Instrument [Line Items]
Number of hedge counterparties (in Counterparties)							2													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											32.7
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)								(76,000)									$ (2,100,000)
Debt Instrument, Interest Rate, Stated Percentage									2.875%
Debt Instrument, Face Amount				$ 22,300,000								22,337,000					$ 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	(152,784,000)
May 2015 Notes [Member]
Debt Instrument [Line Items]
Convertible Debt							$ 155,300,000
Unamortized discount of liability component											$ 0	(1,815,000)
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											$ 5.23
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											$ 0	155,050,000			$ 155,100,000
Debt conversion, shares issued (in Shares) | shares		5.2
Debt instrument, increase, additional borrowings											$ 0	(200,000)
Purchased Call Options [Member]
Debt Instrument [Line Items]
Purchased call options cost							$ 20,800,000
Deferred taxes included in purchased call options cost							$ 7,200,000
Warrants [Member]
Debt Instrument [Line Items]
Convertible notes, conversion price (in Dollars per Share) | $ / shares											$ 6.15
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	$ 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	0
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										232,835,000	276,228,000									300,000,000
Adjustments to additional paid in capital, equity component of convertible debt												18,689,000
Unamortized discount of liability component	(3,100,000)										$ (13,612,000)	(23,772,000)		$ (14,100,000)							$ (29,700,000)
Deferred issuance costs	900,000													$ 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)											2 years 1 month 3 days
Net proceeds from the issuance of convertible notes					$ 290,200,000
Debt Instrument, Repurchase Amount	53,600,000
Debt instrument, repurchase amount paid	43,700,000
Debt Instrument, Face Amount											$ 246,447,000	$ 300,000,000
Conversion Rate per $1,000 Principal Amount (in Ratio)					109.1048
Gains (Losses) 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%