Shareholders' Equity Common Stock Repurchase Plans (Details) - USD ($) $ / shares in Units, shares in Thousands	1 Months Ended				3 Months Ended	12 Months Ended
	Feb. 28, 2021	Oct. 31, 2019	Mar. 31, 2019	Nov. 30, 2018	Mar. 31, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Equity, Class of Treasury Stock [Line Items]
Common stock repurchase amount						$ 39,748,000	$ 111,457,000	$ 95,308,000
Common Stock | February 2021 Stock Repurchase Program | Subsequent Event
Equity, Class of Treasury Stock [Line Items]
Treasury stock, value	$ 75,000,000.0
Percent of common shares outstanding, expected to be delivered	3.20%
Common Stock | October 2019 Stock Repurchase Program
Equity, Class of Treasury Stock [Line Items]
Treasury stock, value		$ 100,000,000.0
Percent of common shares outstanding, expected to be delivered		3.90%
Common stock repurchase amount					$ 39,700,000
Average cost per share of treasury stock acquired (usd per share)					$ 13.65
Acquisition of treasury stock (in shares)					2,900
Common Stock | March 2019 Stock Repurchase Program
Equity, Class of Treasury Stock [Line Items]
Treasury stock, value					$ 100,000,000.0
Percent of common shares outstanding, expected to be delivered			3.50%
Common stock repurchase amount						$ 100,000,000.0
Average cost per share of treasury stock acquired (usd per share)						$ 16.28
Acquisition of treasury stock (in shares)						6,100
Common Stock | November 2018 Stock Repurchase Program
Equity, Class of Treasury Stock [Line Items]
Treasury stock, value				$ 75,000,000.0
Percent of common shares outstanding, expected to be delivered				2.70%
Common stock repurchase amount							$ 75,000,000.0
Average cost per share of treasury stock acquired (usd per share)							$ 15.57
Acquisition of treasury stock (in shares)							706	4,100