Shareholders' Equity (Reconciliation of Basic and Diluted EPS) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Schedule of Earnings Per Share, Basic and Diluted [Line Items]
Net income	$ 58,309	$ 56,584	$ 112,445	$ 113,723
Preferred Stock dividends	1,469	1,469	2,938	2,938
Less: Net income allocated to participating shareholders	496	467	955	937
Net income attributable to common shareholders	$ 56,344	$ 54,648	$ 108,552	$ 109,848
Weighted average number of common shares outstanding - basic	166,188	165,736	165,966	165,574
Basic earnings per common share (in dollars per share)	$ 0.34	$ 0.33	$ 0.65	$ 0.66
Net Income (Loss) Available to Common Stockholders, Diluted	$ 56,344	$ 54,648	$ 108,552	$ 109,848
Weighted average number of common shares outstanding - diluted	166,807	166,277	166,563	166,089
Diluted earnings per common share (in dollars per share)	$ 0.34	$ 0.33	$ 0.65	$ 0.66
Employee Stock Option
Schedule of Earnings Per Share, Basic and Diluted [Line Items]
Weighted average number of common shares outstanding - diluted	619	541	597	515