Earnings Per Common Share (Computation Of Basic And Diluted Earnings (Loss) Per Common Share) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended				9 Months Ended				12 Months Ended
	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012		Dec. 31, 2012
NUMERATORS:
Net income	$ 23,477		$ 25,153		$ 73,091		$ 73,933		$ 101,891
Dividends and undistributed earnings allocated to participating securities	196	[1]	170	[1]	576	[1]	499	[1]
Net earnings available to common shareholders	$ 23,281		$ 24,983		$ 72,515		$ 73,434
DENOMINATORS:
Weighted average number of common shares outstanding - basic	111,912		111,899		111,934		111,928
Effect of potentially dilutive common shares	283	[2]	252	[2]	220	[2]	231	[2]
Weighted average number of common shares outstanding - diluted	112,195		112,151		112,154		112,159
EARNINGS PER COMMON SHARE:
Basic (in usd per share)	$ 0.21		$ 0.22		$ 0.65		$ 0.66
Diluted (in usd per share)	$ 0.21		$ 0.22		$ 0.65		$ 0.65

[1] Represents dividends paid and undistributed earnings allocated to nonvested restricted stock awards.

[2] Represents the effect of the assumed exercise of stock options, vesting of non-participating restricted shares, and vesting of restricted stock units, based on the treasury stock method.