Stock Options - Summary of Stock Option Activity (Detail) - Employee Stock Option $ / shares in Units, shares in Thousands, $ in Millions	9 Months Ended
	Sep. 30, 2016 USD ($) $ / shares shares
Shares
Outstanding at December 31, 2015 (in shares) | shares	2,723
Granted (in shares) | shares	11
Exercised (in shares) | shares	0
Forfeited and expired (in shares) | shares	(605)
Outstanding at September 30, 2016 (in shares) | shares	2,129
Expected to vest at September 30, 2016 (in shares) | shares	624
Exercisable at September 30, 2016 (in shares) | shares	1,486
Weighted- Average Exercise Price
Outstanding at December 31, 2015 (in dollars per share) | $ / shares	$ 27.88
Granted (in dollars per share) | $ / shares	10.85
Exercised (in dollars per share) | $ / shares	0.00
Forfeited and expired (in dollars per share) | $ / shares	36.26
Outstanding at September 30, 2016 (in dollars per share) | $ / shares	25.41
Expected to vest at September 30, 2016 (in dollars per share) | $ / shares	25.97
Exercisable at September 30, 2016 (in dollars per share) | $ / shares	$ 25.21
Weighted- Average Remaining Contractual Term (years)
Outstanding at September 30, 2016	2 years 6 months 11 days
Expected to vest at September 30, 2016	3 years 11 months 12 days
Exercisable at September 30, 2016	1 year 10 months 28 days
Aggregate Intrinsic Value
Outstanding at September 30, 2016 | $	$ 0
Expected to vest at September 30, 2016 | $	0
Exercisable at September 30, 2016 | $	$ 0