Share Repurchase (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2019	Jan. 31, 2020	Nov. 07, 2018
Equity, Class of Treasury Stock [Line Items]
Total number of share repurchases	1,755,160	1,131,124	2,673,967	2,365,451	5,219,123
Total cost of share repurchases	$ 59,764	$ 56,758	$ 100,019	$ 115,933	$ 217,899
Average price paid per share	$ 34.05	$ 50.18	$ 37.40	$ 49.01	$ 41.75
Authorized On January Thirty-One Two-Thousand Twenty [Member] | Subsequent Event [Member]
Equity, Class of Treasury Stock [Line Items]
Authorized amount for repurchase						$ 300,000
Maximum | Authorized on November 7, 2018
Equity, Class of Treasury Stock [Line Items]
Authorized amount for repurchase							$ 300,000
Remaining authorized amount for repurchase	$ 82,100		$ 82,100		$ 82,100