Shareholders' Equity (Reconciliation of Basic and Diluted EPS) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Schedule of Earnings Per Share, Basic and Diluted [Line Items]
Net income	$ 54,136	$ 57,139
Preferred Stock dividends	1,469	1,469
Less: Net income allocated to participating shareholders	387	407
Net income attributable to common shareholders	$ 52,280	$ 55,263
Weighted average number of common shares outstanding - basic	165,745	165,411
Basic earnings per common share (in dollars per share)	$ 0.32	$ 0.33
Net Income (Loss) Available to Common Stockholders, Diluted	$ 52,280	$ 55,263
Weighted average number of common shares outstanding - diluted	166,239	166,003
Diluted earnings per common share (in dollars per share)	$ 0.31	$ 0.33
Employee Stock Option
Schedule of Earnings Per Share, Basic and Diluted [Line Items]
Weighted average number of common shares outstanding - diluted	494	592