Stockholders' Equity - Computation of Basic and Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2021	Sep. 30, 2020
Numerator:
Net income	$ 73,795	$ 61,366	$ 48,545	$ 42,710	$ 47,218	$ 42,402	$ 183,705	$ 132,331
Denominator:
Basic weighted average shares outstanding	115,344,015			115,773,030			115,455,543	115,921,463
Effect of dilutive securities:
Diluted weighted average shares outstanding	115,625,760			116,134,623			115,767,426	116,280,807
Basic earnings per share	$ 0.64			$ 0.37			$ 1.59	$ 1.14
Diluted earnings per share	$ 0.64			$ 0.37			$ 1.59	$ 1.14
Stock appreciation rights [Member]
Effect of dilutive securities:
Dilutive securities	171,514			202,113			190,680	187,767
Restricted stock [Member]
Effect of dilutive securities:
Dilutive securities	110,231			159,480			121,203	171,577