Stockholders' Equity - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands		1 Months Ended	6 Months Ended
	Mar. 15, 2018	Feb. 28, 2018	Jun. 30, 2018	Jun. 30, 2019	Nov. 30, 2015
Stockholders Equity Note [Line Items]
Dividends paid	$ 154,000		$ 153,967
Par value of common stock				$ 1.00
Dividend Declared [Member]
Stockholders Equity Note [Line Items]
Dividend record date		Mar. 05, 2018
Dividend payable nature		special
Special dividend declared per share		$ 10.00
2015 Repurchase Program
Stockholders Equity Note [Line Items]
Aggregate amount of common stock authorized for repurchase					$ 400,000
2018 Repurchase Program
Stockholders Equity Note [Line Items]
Aggregate amount of common stock authorized for repurchase			$ 400,000
Remaining authorized repurchases under share repurchase program				$ 178,300