Calculation of Basic and Diluted Net Income (Loss) per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
BASIC EPS:
Net income (loss)	$ (58,658)	$ (225,978)	$ (18,975)	$ 9,125	$ 57,583	$ 15,976	$ 54,283	$ 34,822	$ (294,486)	$ 162,664	$ 188,009
Adjust for (income) loss attributed to holders of non-vested restricted stock									3,022	(1,663)	(1,859)
Income (loss) attributed to common stockholders									$ (291,464)	$ 161,001	$ 186,150
Weighted average number of common shares outstanding, excluding non-vested shares of restricted stock									145,416	144,066	144,356
Basic net income (loss) per common share	$ (0.40)	$ (1.54)	$ (0.13)	$ 0.06	$ 0.39	$ 0.11	$ 0.37	$ 0.24	$ (2.00)	$ 1.12	$ 1.29
DILUTED EPS:
Income (loss) attributed to common stockholders									$ (291,464)	$ 161,001	$ 186,150
Weighted average number of common shares outstanding, excluding non-vested shares of restricted stock									145,416	144,066	144,356
Add dilutive effect of potential common shares										1,310	947
Weighted average number of diluted common shares outstanding									145,416	145,376	145,303
Diluted net income (loss) per common share	$ (0.40)	$ (1.54)	$ (0.13)	$ 0.06	$ 0.39	$ 0.11	$ 0.37	$ 0.24	$ (2.00)	$ 1.11	$ 1.28
Potentially dilutive securities excluded as anti-dilutive									7,781	1,088	2,447