Outstanding Common Stock Equivalents That Were Anti-Dilutive Tickmarks (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Earnings Per Share [Abstract]
Anti-dilutive Non-Vested Stock Weighted Average Grant Date Fair Value	$ 26.20	$ 39.48	$ 48.66