Components of Basic and Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2016		Mar. 31, 2015		Mar. 31, 2014
Earnings Per Share [Abstract]
Net earnings (loss) available to common shareholders	$ (81,787)	$ (19,509)	$ (43,835)	$ (15,052)	$ (9,076)	$ (160,694)	$ 60,907	$ 43,673	$ (160,183)		$ (65,190)		$ 140,255
Weighted average outstanding shares of common stock, basic									46,981,102		48,658,840		49,392,749
Dilutive effect of stock options and restricted stock													287,365
Weighted average common stock and equivalents									46,981,102		48,658,840		49,680,114
Earnings (loss) per share, basic	$ (1.74)	$ (0.42)	$ (0.93)	$ (0.32)	$ (0.19)	$ (3.31)	$ 1.23	$ 0.88	$ (3.41)	[1]	$ (1.34)	[1]	$ 2.84	[1]
Earnings (loss) per share, diluted	$ (1.74)	$ (0.42)	$ (0.93)	$ (0.32)	$ (0.19)	$ (3.31)	$ 1.22	$ 0.88	$ (3.41)	[2]	$ (1.34)	[2]	$ 2.82	[2]
Antidilutive options and restricted stock shares									489,325		284,635		34,486

[1] The company calculates “Loss per share, basic” by dividing “Net loss available to common shareholders” by “Weighted average outstanding share of common stock, basic”.

[2] The company calculates “Loss per share, diluted” by dividing “Net loss available to common shareholders” by “Weighted average common stock and equivalents”.