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				6 Months Ended				12 Months Ended
	Jun. 30, 2013		Jun. 30, 2012		Jun. 30, 2013		Jun. 30, 2012		Dec. 31, 2012
NUMERATORS:
Net income	$ 26,253		$ 23,277		$ 49,614		$ 48,780		$ 101,891
Dividends and undistributed earnings allocated to participating securities	197	[1]	162	[1]	380	[1]	329	[1]
Net earnings available to common shareholders	$ 26,056		$ 23,115		$ 49,234		$ 48,451
DENOMINATORS:
Weighted average number of common shares outstanding - basic	111,954		111,897		111,946		111,943
Effect of potentially dilutive common shares	191	[2]	181	[2]	187	[2]	177	[2]
Weighted average number of common shares outstanding - diluted	112,145		112,078		112,133		112,120
EARNINGS PER COMMON SHARE:
Basic (in usd per share)	$ 0.23		$ 0.21		$ 0.44		$ 0.43
Diluted (in usd per share)	$ 0.23		$ 0.21		$ 0.44		$ 0.43

[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.