Convertible Notes (Summary of Convertible Notes) (Detail)			1 Months Ended	3 Months Ended	9 Months Ended
		Feb. 11, 2014	Jan. 31, 2012 USD ($)	Sep. 30, 2016 USD ($) $ / shares	Sep. 30, 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	$ 0	$ 24,966,000
Convertible Notes Payable, Carrying Value				$ 234,895,000	$ 234,895,000	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%	3.75%
Convertible notes, conversion price (in Dollars per Share) | $ / shares				$ 5.72	$ 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	$ 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				$ 246,447,000
Convertible Notes Payable, Carrying Value	[2]			234,895,000	$ 234,895,000	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	$ 0
Convertible Notes Payable, Carrying Value						$ 24,966,000

[1] unaudited

[2] {F|ahBzfndlYmZpbGluZ3MtaHJkcmoLEgZYTUxEb2MiXlhCUkxEb2NHZW5JbmZvOjAwNjFhMzJkZGMzYzQ5MzE4YzEwYjAyNzhkOTY3ZGUzfFRleHRTZWxlY3Rpb246NkUzQzZCNTU3MEVDMDcxNzQ4N0VCMzIwQjEyNjRDQzcM}

[3] {F|ahBzfndlYmZpbGluZ3MtaHJkcmoLEgZYTUxEb2MiXlhCUkxEb2NHZW5JbmZvOjAwNjFhMzJkZGMzYzQ5MzE4YzEwYjAyNzhkOTY3ZGUzfFRleHRTZWxlY3Rpb246QTEwQUYzMzJCQURENTlERkQzNzVCMzIwQjFFOTRCOEEM}