Equity-Based Compensation (Narrative) (Details) (USD $)	6 Months Ended		12 Months Ended	3 Months Ended	6 Months Ended				12 Months Ended	6 Months Ended			12 Months Ended				12 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013	Jun. 30, 2014 Former President and Chief Operating Officer	Jun. 30, 2014 2005 Equity Incentive Plan	Jun. 30, 2014 Performance Stock Units	Jun. 30, 2014 Management Stock Purchase Plan	Jun. 30, 2013 Management Stock Purchase Plan	Dec. 31, 2013 Management Stock Purchase Plan	Jun. 30, 2014 Minimum Performance Stock Units	Jun. 30, 2014 Maximum Performance Stock Units	Jun. 30, 2014 Unvested Restricted Stock Units	Dec. 31, 2013 Unvested Restricted Stock Units	Dec. 31, 2012 Awarded January 2012 Performance Stock Units	Jun. 30, 2014 Awarded January 2012 Performance Stock Units	Jan. 31, 2012 Awarded January 2012 Performance Stock Units	Dec. 31, 2013 Awarded January 2013 Performance Stock Units	Jun. 30, 2014 Awarded January 2013 Performance Stock Units	Jan. 31, 2013 Awarded January 2013 Performance Stock Units	Jan. 31, 2014 Awarded January 2014 Performance Stock Units	Jun. 30, 2014 Awarded June 2014 Performance Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Typical vesting period, in years	4 years
Maximum number of shares that may be issued under the Plan					3,000,000
Maximum number of shares that may be issued in connection with grants of incentive stock options and rights					900,000
Performance stock units outstanding															280,000	295,000		246,000	304,000	212,000	19,000
Performance stock unit grant-date fair value																$ 4,152,000			$ 4,123,000	$ 3,914,000	$ 319,000
Percentage of target performance stock units earned														58.30%			50.00%
Performance stock units earned														163,200			123,000
Performance stock units target awards														280,000			246,000
Performance stock unit vesting period										1 year	3 years
MSPP company matching portion, vesting age	60 years
Years of service						5 years
Average closing price, number of days trailing						90 days	200 days
Accrues interest							2.00%
Number of restricted stock units credited to participant accounts	726,915		614,888				112,027	189,291				62,232	47,268
Weighted average fair value of per unit awarded							$ 16.85		$ 15.97
Disbursements of MSPP	$ 2,120,000	$ 531,000		$ 1,725,000