Earnings Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Earnings Per Share [Abstract]
Net (Loss) to Common Stockholders, Basic EPS	$ 27,445	$ (19,789)	$ (49,997)	$ (22,267)	$ (38,230)	$ 15,068	$ 12,636	$ (5,150)	$ (64,608)	$ (15,677)	$ 46,199
Net (Loss) Income to Common Stockholders, Effect of dilutive securities											1,188
Net (Loss) Income to Common Stockholders, Diluted EPS									$ (64,608)	$ (15,677)	$ 47,387
Average Shares, Basic EPS	98,823	98,739	98,635	98,537	98,444	98,353	98,271	98,185	98,739	98,314	96,764
Average Shares, Effect of dilutive securities											3,715
Average Shares, Diluted EPS	103,141	98,739	98,635	98,537	98,444	102,331	102,205	98,185	98,739	98,314	100,479
(Loss) income per Share, Basic EPS	$ 0.28	$ (0.20)	$ (0.51)	$ (0.23)	$ (0.39)	$ 0.15	$ 0.13	$ (0.05)	$ (0.65)	$ (0.16)	$ 0.48
(Loss) income per Share, Effect of dilutive securities											(0.01)
(Loss) income per Share, Diluted EPS	$ 0.27	$ (0.20)	$ (0.51)	$ (0.23)	$ (0.39)	$ 0.15	$ 0.13	$ (0.05)	$ (0.65)	$ (0.16)	$ 0.47