Earnings Per Share - Computation of Basic and Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Numerator:
Income available to common stockholders									$ 207,187	$ 269,911	$ 187,191
Denominator:
Basic weighted-average shares outstanding (shares)									140,851,444	148,183,431	154,134,411
Effect of dilutive shares:
Stock options and unvested restricted stock units (shares)									542,783	821,259	950,955
Diluted weighted-average shares outstanding (shares)									141,394,227	149,004,690	155,085,366
Basic
Basic (in dollars per share)	$ 0.85	$ 0.45	$ 0.18	$ 0	$ 0.70	$ 0.43	$ 0.42	$ 0.28	$ 1.47	$ 1.82	$ 1.21
Diluted
Diluted (in dollars per share)	$ 0.85	$ 0.44	$ 0.18	$ 0	$ 0.70	$ 0.43	$ 0.42	$ 0.28	$ 1.47	$ 1.81	$ 1.21
Antidilutive stock options not included in diluted earnings per share (in shares)									2,636,982	1,645,816	3,288,340