Common Stock Repurchase Programs - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended					9 Months Ended	12 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Sep. 30, 2019	Dec. 31, 2018	Aug. 31, 2018
Common Stock [Line Items]
Common stock authorized for repurchase								$ 500,000
Common stock repurchased	$ 415	$ 65,527	$ 78,982	$ 250,000	$ 52,160	$ 144,900	$ 250,000
Common Stock [Member]
Common Stock [Line Items]
Common stock repurchased		$ 25	$ 25	$ 42	$ 12
Repurchased common stock, shares	20,000	2,508,000	2,525,000	4,224,000	1,155,000	5,100,000
Restricted Stock [Member]
Common Stock [Line Items]
Number of shares withheld to satisfy minimum statutory tax withholding obligations						83,341
Amount withheld to satisfy minimum statutory tax withholding obligations						$ 2,100