Shareholders' Equity - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	Dec. 12, 2018	May 01, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018
Accelerated Share Repurchases [Line Items]
Shares repurchased, authorized amount			$ 147,500	$ 100,000
Shares repurchased, number of shares received initially (in shares)				13,796,696	13,796,696
Fair value of common stock repurchased			477,572	$ 477,572
Accelerated Share Repurchases, Settlement (Payment) or Receipt				$ 20,000
Common Stock, Shares, Outstanding				279,583,006	282,047,861
Common Stock, Shares Authorized				560,000,000	560,000,000
Common Stock, Par or Stated Value Per Share				$ 0.10	$ 0.10
Accelerated Share Repurchase Agreement [Member]
Accelerated Share Repurchases [Line Items]
Fair value of common stock repurchased				$ 80,000
Treasury Stock, Shares, Acquired	2,910,150
Repurchase Agreements [Member]
Accelerated Share Repurchases [Line Items]
Shares repurchased, authorized amount			$ 100,000
Subsequent Event [Member] | Third Accelerated Share Repurchase Agreement [Member]
Accelerated Share Repurchases [Line Items]
Shares repurchased, authorized amount		$ 372,500
Shares repurchased, number of shares received initially (in shares)		500,000,000.0