Equity Compensation Plans (Summary of Unvested Restricted Shares) (Detail) - Restricted Stock shares in Thousands	12 Months Ended
	Dec. 31, 2016 $ / shares shares
Shares:
Nonvested at December 31, 2015 (in shares) | shares	343
Granted (in shares) | shares	84
Vested (in shares) | shares	(98)
Forfeited/Cancelled (in shares) | shares	(33)
Nonvested December 31, 2016 (in shares) | shares	296
Weighted-Average Grant-Date Fair Value:
Nonvested at December 31, 2015 (in dollars per share) | $ / shares	$ 24.01
Granted (in dollars per share) | $ / shares	49.70
Vested (in dollars per share) | $ / shares	16.96
Forfeited/Cancelled (in dollars per share) | $ / shares	20.92
Nonvested December 31, 2016 (in dollars per share) | $ / shares	$ 34.01