Earnings Per Share - Computations of Class A Basic and Diluted Earnings (Loss) per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Antidilutive securities excluded from computation of earnings per share	9,100,000	9,000,000	400,000	9,000,000
Numerator for basic and diluted earnings per share:
Net earnings (loss) attributable to controlling interest	$ (12,595)	$ (29,828)	$ 156,045	$ (9,955)
Less: earnings allocated to participating securities	(44)	(29)	(154)	(74)
Numerator for basic EPS - net income (loss) attributable to common stockholders	(12,639)	(29,857)	155,891	(10,029)
Add back allocation of earnings to participating securities	44	29	154	74
Add back convertible senior notes interest	0	0	11,305	0
Reallocation of earnings to participating securities considering potentially dilutive securities	(44)	(29)	(151)	(74)
Numerator for diluted earnings per share - net income (loss) attributable to common stockholders	$ (12,639)	$ (29,857)	$ 167,199	$ (10,029)
Denominator for earnings per share:
Class A common stock - basic (in shares)	97,460,492	87,370,979	97,464,012	87,146,465
Class A common stock - diluted (in shares)	97,460,492	87,370,979	105,788,848	87,146,465
Calculation of basic and diluted earnings (loss) per share:
Basic (in dollars per share)	$ (0.13)	$ (0.34)	$ 1.60	$ (0.12)
Diluted (in dollars per share)	(0.13)	(0.34)	1.58	(0.12)
Dividends declared per Class A common share (in dollars per share)	$ 0.42	$ 0.42	$ 1.27	$ 1.25
Restricted stock awards
Denominator for earnings per share:
Add dilutive effect (in shares)	0	0	153,444	0
Restricted stock units
Denominator for earnings per share:
Add dilutive effect (in shares)	0	0	652	0
Convertible senior notes
Denominator for earnings per share:
Add dilutive effect (in shares)	0	0	8,170,740	0