Shareholders' Equity - Additional Information (Detail) - USD ($)	3 Months Ended				6 Months Ended		12 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2014	Dec. 31, 2018	May 08, 2018
Stockholders Equity Note Disclosure [Line Items]
Payments for Repurchase of Common Stock					$ 150,000,000.0	$ 300,000,000.0
Common Stock, Dividends, Per Share, Cash Paid	$ 0.18	$ 0.18	$ 0.175	$ 0.35
Dividends payable	$ 30,200,000				30,200,000			$ 30,800,000
May 2018 Share Repurchase Program [Member]
Stockholders Equity Note Disclosure [Line Items]
Repurchase of shares of our common stock up to a maximum aggregate value									$ 750,000,000.0
Common stock authorized for repurchase, expiration date							May 31, 2021
December 2014 Share Repurchase Program
Stockholders Equity Note Disclosure [Line Items]
Share repurchase program remaining available amount	$ 250,000,000.0				$ 250,000,000.0