Stock-based Compensation (Details) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share Based Compensation Expense	$ 34,914	$ 30,588	$ 28,853
Full Value Awards [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share Based Compensation Arrangement By Share Based Payment Award Number Of Shares Authorized	6,000,000
Share Based Compensation Shares Available For Grant	4,672,000
Not Full Value Awards [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share Based Compensation Arrangement By Share Based Payment Award Number Of Shares Authorized	12,000,000
Out Performance Plan 2013 [Member]
Out Performance Plan [Abstract]
Out of performance plan notional amount	40,000
Award vesting in three years	33.00%
Award versting in four years	33.00%
Award vesting in five years	34.00%
Fair Value Of Awards Granted	6,814
Award Amortization Period	5 years
Out Performance Plan 2013 [Member] | Absolute [Member]
Out Performance Plan [Abstract]
Required Shareholder Return Per Two Year	14.00%
Required Shareholder Return Three Year	21.00%
Out Performance Plan 2013 [Member] | Relative [Member]
Out Performance Plan [Abstract]
Required Shareholder Return Under Relative Component	6.00%
Percentage Of Shareholder Return Under Which No Awards Will Be Earned	0.00%
Out Performance Plan 2012 [Member]
Out Performance Plan [Abstract]
Out of performance plan notional amount	40,000
Award vesting in three years	33.00%
Award versting in four years	33.00%
Award vesting in five years	34.00%
Fair Value Of Awards Granted	12,250
Award Amortization Period	5 years
Out Performance Plan 2012 [Member] | Absolute [Member]
Out Performance Plan [Abstract]
Required Shareholder Return Per Year	7.00%
Required Shareholder Return Three Year	21.00%
Out Performance Plan 2012 [Member] | Relative [Member]
Out Performance Plan [Abstract]
Required Shareholder Return Under Relative Component	6.00%
Percentage Of Shareholder Return Under Which No Awards Will Be Earned	0.00%
Employee Stock Option [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share Based Compensation Expense	8,234	8,638	8,794
Out Performance Plan [Abstract]
Compensation Cost Not Yet Recognized	5,398
Compensation Cost Recognition Period	1 year 3 months 20 days
Stock options expiration term	10 years
Award Vesting Period	4 years
Share Based Compensation Employee Stock Purchase Plan Activity [Abstract]
Grant Date Fair Value Of Options (in dollars per shares)	$ 17.18	$ 17.50	$ 21.42
Cash Received From Exercise Of Stock Options	5,915	9,546	23,736
Total Intrinsic Value Of Options Excercised	3,386	40,887	39,348
Restricted Stock Units RSU [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share Based Compensation Expense	1,344	1,604	1,814
Out Performance Plan [Abstract]
Compensation Cost Not Yet Recognized	1,781
Compensation Cost Recognition Period	1 year 7 months 6 days
Dividends Paid On Nonvested Units	110	200	185
Fair Value Of Awards Granted	857	929	1,042
Award Vesting Period	4 years
Fair Value Of Awards Vested	1,194	1,864	2,031
Restricted Operating Partnership Units Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share Based Compensation Expense	22,110	17,520	17,505
Out Performance Plan [Abstract]
Compensation Cost Not Yet Recognized	25,971
Compensation Cost Recognition Period	1 year 9 months 18 days
Dividends Paid On Nonvested Units	2,598	3,203	2,567
Fair Value Of Awards Granted	31,947	16,464	18,727
Award Vesting Period	4 years
Fair Value Of Awards Vested	16,404	15,014	10,260
Out Performance Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share Based Compensation Expense	3,226	2,826	740
Out Performance Plan [Abstract]
Compensation Cost Not Yet Recognized	$ 10,065
Compensation Cost Recognition Period	1 year 10 months 24 days