Quarterly Results of Operations - Summary of Quarterly Results of Operations (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Quarterly Financial Data [Abstract]
Total revenues	$ 444,143	$ 297,330	$ 187,473	$ 66,771	$ 331,576	$ 219,393	$ 412,433	$ 310,857	$ 995,717	$ 1,274,259	$ 1,487,153
Total expenses	417,229	465,795	565,706	343,422	548,252	364,124	427,955	371,425	1,792,152	1,711,756	1,625,029
Total other gains (losses)	(74)	10,282	(1,351)	(2,240)	8,485	13,173	523	10,890	6,617	33,071	18,536
Loss before income taxes	26,840	(158,183)	(379,584)	(278,891)	(208,191)	(131,558)	(14,999)	(49,678)	(789,818)	(404,426)	(119,340)
Income tax expense (benefit)	49,069	(56,357)	(147,183)	(106,189)	(91,056)	(54,630)	23,120	(18,670)	(260,660)	(141,236)	(9,012)
Net loss	$ (22,229)	$ (101,826)	$ (232,401)	$ (172,702)	$ (117,135)	$ (76,928)	$ (38,119)	$ (31,008)	(529,158)	(263,190)	$ (110,328)
Basic and diluted loss per common and common equivalent share (in dollars per share)	$ (0.61)	$ (2.82)	$ (6.49)	$ (4.85)	$ (3.16)	$ (2.04)	$ (1.01)	$ (0.82)
Goodwill impairment	$ 13,200	$ 91,000	$ 215,400		$ 151,000		$ 56,500		$ 319,551	$ 207,557