Debt Facilities - Additional Information (Detail) (USD $)	1 Months Ended	9 Months Ended			1 Months Ended		3 Months Ended	9 Months Ended			9 Months Ended	1 Months Ended					3 Months Ended	9 Months Ended			9 Months Ended			1 Months Ended	3 Months Ended		9 Months Ended
	Jun. 30, 2009	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013	Jun. 30, 2014 3.00% Convertible subordinated notes [Member]	Sep. 30, 2007 3.00% Convertible subordinated notes [Member]	Jun. 30, 2014 3.00% Convertible subordinated notes [Member]	Sep. 30, 2014 3.00% Convertible subordinated notes [Member]	Dec. 31, 2013 3.00% Convertible subordinated notes [Member]	Sep. 30, 2013 3.00% Convertible subordinated notes [Member]	Sep. 30, 2014 3.00% Convertible subordinated notes [Member] Minimum [Member]	Sep. 30, 2007 3.00% Convertible subordinated notes [Member] Maximum [Member]	Sep. 30, 2007 3.00% Convertible subordinated notes [Member] Initial conversion rate [Member]	Jun. 30, 2014 4.75% Convertible subordinated notes [Member]	May 31, 2014 4.75% Convertible subordinated notes [Member]	Jun. 30, 2009 4.75% Convertible subordinated notes [Member]	Jun. 30, 2014 4.75% Convertible subordinated notes [Member]	Sep. 30, 2014 4.75% Convertible subordinated notes [Member]	Dec. 31, 2013 4.75% Convertible subordinated notes [Member]	Sep. 30, 2013 4.75% Convertible subordinated notes [Member]	Sep. 30, 2014 4.75% Convertible subordinated notes [Member] Condition One [Member] Days	Sep. 30, 2014 4.75% Convertible subordinated notes [Member] Condition Two [Member]	Jun. 30, 2009 4.75% Convertible subordinated notes [Member] Minimum [Member]	Jun. 30, 2009 4.75% Convertible subordinated notes [Member] Initial conversion rate [Member]	Sep. 30, 2014 3.00% and 4.75% Convertible Subordinated Notes [Member]	Sep. 30, 2013 3.00% and 4.75% Convertible Subordinated Notes [Member]	Sep. 30, 2014 3.00% and 4.75% Convertible Subordinated Notes [Member]	Sep. 30, 2013 8.125% senior notes [Member]
Debt Instrument [Line Items]
Convertible Subordinated Notes aggregate principal amount		$ 336,662,000		$ 769,710,000		$ 395,986,000		$ 178,782,000	$ 395,986,000							$ 373,750,000		$ 157,880,000	$ 373,724,000									$ 750,000,000
Convertible debt interest rate						3.00%		3.00%		3.00%						4.75%		4.75%		4.75%
Debt instrument maturity date								Oct. 15, 2014										Jun. 15, 2016
Conversion numerator											4.4616	11.8976	7.436											11.8599
Conversion denominator						1,000										1,000
Conversion price per share												$ 84.05	$ 134.48								$ 109.62		$ 84.32
Convertible Subordinated Notes, converted number of common stock						4,711,283
Exchange value of Convertible Subordinated Notes of aggregate principal amount					217,199,000									215,830,000	215,830,000
Convertible subordinated notes common stock					1,948,578									2,411,851	2,411,851
Cash payment		37,510,000	42,304,000		5,387,000									51,671,000	51,671,000
Loss on debt extinguishment		$ (51,183,000)	$ (93,602,000)				$ 4,210,000										$ 46,973,000								$ 0	$ 0	$ 51,183,000	$ 93,602,000
Company election to satisfy obligation in cash	100.00%
Trading period, in days																					20
Consecutive trading days																					30 days	10 days
Conversion price per share, percentage																					130.00%
Percentage of trading price of Convertible Subordinated Notes, maximum																						98.00%
Debt conversion, maturity date																		Mar. 15, 2016
Capped Call, description		The Capped Call was amended to provide that early exchanges of the 4.75% Convertible Subordinated Notes would not result in the termination of a relative amount of the Capped Call if the Company did not exercise the Capped Call at the time the 4.75% Convertible Subordinated Notes were exchanged.
Subordinated Notes converted into common stock																		1,872,552