Equity Incentive Compensation Plans and Other Long-term Incentive Programs - Stock Options and Nonvested Equity Shares, Equity Awards Granted (Detail) - $ / shares	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Nonvested Equity Shares
Units
Beginning balance (in shares)	2,968,497	2,912,166
Granted (in shares)	2,028,617	1,835,700
Vested (in shares)	(1,455,814)	(1,299,599)
Forfeited or expired (in shares)	(9,488)	(16,487)
Ending balance (in shares)	3,531,812	3,431,780
Weighted Average Grant Date Fair Value
Beginning balance (in dollars per share)	$ 3.81	$ 5.27
Granted (in dollars per share)	1.14	2.64
Vested (in dollars per share)	4.25	5.19
Forfeited or expired (in dollars per share)	3.44	4.74
Ending balance (in dollars per share)	$ 2.10	$ 3.90
Nonvested Performance Cash Units
Units
Beginning balance (in shares)	2,576,062	909,585
Granted (in shares)	3,569,434	2,026,521
Forfeited or expired (in shares)	(49,266)	(67,472)
Ending balance (in shares)	6,096,230	2,868,634
Weighted Average Grant Date Fair Value
Ending balance (in dollars per share)	$ 0.19	$ 2.21
Director
Units
Beginning balance (in shares)	796,103	311,237
Granted (in shares)	0	14,704
Vested (in shares)	0	(14,704)
Ending balance (in shares)	796,103	311,237
Weighted Average Grant Date Fair Value
Beginning balance (in dollars per share)	$ 3.27	$ 7.26
Granted (in dollars per share)	0	2.21
Vested (in dollars per share)	0	2.21
Ending balance (in dollars per share)	$ 3.27	$ 7.26