Capital Stock - Common Stock (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Feb. 28, 2021
Class of Stock [Line Items]
Stock repurchase program, authorized amount					$ 250,000,000
Stock repurchased during period (in shares)	0	0	161,000	1,400,000
Stock repurchased during period, average price (in dollars per share)			$ 11.39	$ 15.34
Stock repurchased during period			$ 1,828,000	$ 22,066,000
Remaining authorized repurchase amount	$ 226,000,000		226,000,000
Common dividends declared	$ 79,268,000	$ 68,477,000	$ 228,284,000	$ 232,007,000
Dividends declared per share of common stock (usd per share)	$ 0.33	$ 0.30	$ 0.96	$ 1.10
Regular Dividend
Class of Stock [Line Items]
Common dividends declared	$ 79,000,000	$ 68,000,000	$ 228,000,000	$ 232,000,000