Shareholders' Equity Common Stock Repurchase Plans (Details) - USD ($) $ / shares in Units, shares in Millions	1 Months Ended		12 Months Ended
	Nov. 30, 2018	Nov. 30, 2017	Dec. 31, 2018	Dec. 31, 2016
Equity, Class of Treasury Stock [Line Items]
Common stock repurchase amount			$ 95,308,000	$ 18,545,000
Common Stock | November 2017 Stock Repurchase Program
Equity, Class of Treasury Stock [Line Items]
Treasury stock, value		$ 50,000,000.0
Common stock repurchase amount			$ 31,500,000
Average cost per share of treasury stock acquired (usd per share)			$ 16.71
Acquisition of treasury stock (in shares)			(1.9)
Percent of common shares outstanding, expected to be delivered		2.30%
Common Stock | November 2018 Stock Repurchase Program
Equity, Class of Treasury Stock [Line Items]
Treasury stock, value	$ 75,000,000.0
Common stock repurchase amount			$ 63,700,000
Average cost per share of treasury stock acquired (usd per share)			$ 15.49
Acquisition of treasury stock (in shares)			(4.1)
Percent of common shares outstanding, expected to be delivered	2.70%
Stock Repurchase Program, Additional Amount Authorized	$ 11,322,254