Convertible Notes (Summary of Convertible Notes) (Detail)			1 Months Ended	3 Months Ended
		Feb. 11, 2014	Jan. 31, 2012 USD ($)	Mar. 31, 2016 USD ($) $ / shares	Dec. 31, 2015 USD ($)		May. 01, 2015 USD ($)	Feb. 17, 2015 USD ($)	Feb. 12, 2014 USD ($) $ / 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
Term loan payable	[1]			0	$ 24,966,000
Convertible Notes Payable, Carrying Value				$ 230,850,000	253,828,000
Series 2012 Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage			2.875%
Convertible Notes, Principal Balance Outstanding								$ 22,300,000		$ 48,300,000	$ 180,000,000
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
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
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, Maturity Date (Date)				Feb. 01, 2018
Convertible Notes, Principal Balance Outstanding				$ 246,447,000	246,447,000				$ 246,447,000
Convertible Notes Payable, Carrying Value	[2]			$ 230,850,000	228,862,000	[3]
Term Loan. [Member]
Debt Instrument [Line Items]
Convertible Notes, Maturity Date (Date)				Feb. 15, 2016
Convertible Notes, Principal Balance Outstanding				$ 0
Convertible Notes Payable, Carrying Value					$ 24,966,000

[1] unaudited

[2] * Effective January 1, 2016, the Company adopted ASU 2015-03 and changed its method of presentation relating to debt issuance cost. Prior to 2016, the Company's policy was to present these costs in other assets on the consolidated balance sheet, net of accumulated amortization. Beginning in 2016, the Company has presented these fees as a direct deduction to the related debt. As a result, we reclassified $3.5 million and $4.0 million of deferred financing costs as of March 31, 2016 and December 31, 2015, respectively, from other assets, which are currently presented as a direct deduction to the February 2018 Notes.

[3] * Effective January 1, 2016, the Company adopted ASU 2015-03 and changed its method of presentation relating to debt issuance cost. Prior to 2016, the Company's policy was to present these costs in other assets on the consolidated balance sheet, net of accumulated amortization. Beginning in 2016, the Company has presented these fees as a direct deduction to the related debt. As a result, we reclassified $3.5 million and $4.0 million of deferred financing costs as of March 31, 2016 and December 31, 2015, respectively, from other assets, which are currently presented as a direct deduction to the February 2018 Notes.