Capital Stock - Common Stock (Detail) - USD ($) $ / shares in Units, shares in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Feb. 28, 2018
Class of Stock [Line Items]
Stock repurchase program, authorized amount				$ 100,000,000
Stock repurchased during period (in shares)		883
Stock repurchased during period, average price (in dollars per share)		$ 16.81
Stock repurchased during period	$ 0	$ 14,834,000	$ 0
Remaining authorized repurchase amount	85,000,000
Common dividends declared	$ (376,839,000)	$ (375,017,000)	$ (376,579,000)
Dividends declared per share of common stock (usd per share)	$ 2.00	$ 2.00
Regular Dividend
Class of Stock [Line Items]
Common dividends declared	$ (377,000,000)	$ (375,000,000)