Earnings Per Share - Schedule of Basic and Diluted Earnings Per Share (Detail) - USD ($) 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	Mar. 31, 2013	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Earnings Per Share [Abstract]
Net income	$ (15,320)	$ 2,412	$ 9,953	$ 14,823	$ 33,238	$ 41,277	$ 28,654	$ 18,371	$ 75,256	$ 11,868	$ 121,540	$ 75,256
Weighted Average Number of Shares Outstanding, Basic	53,323	53,321	53,303	53,416	53,838	53,801	53,733	53,505		53,344	53,719	53,035
Weighted Average Number of Shares Outstanding, Diluted										53,601	54,296	53,409