Common Share Capitalization (Narrative) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Feb. 06, 2018
Common Stock Capitalization [Line Items]
Dividends declared (in usd per share)	$ 0.41	$ 0.45
Payments of Dividends	$ (12,850)	$ (14,821)
Common Shares Issued And Outstanding Upon Conversion of All Convertible Securities	31,096,923	32,845,754
Stock Repurchase Program, Number of Shares Authorized to be Repurchased			1,550,000
Shares repurchased	943,897	130,488
Stock Repurchased and Retired During Period, Value	$ 13,966	$ 2,052
Stock Repurchases, Average Price Per Share	$ 14.80