Share-based Compensation-Additional Information (Details) (USD $)	3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended		12 Months Ended	9 Months Ended			12 Months Ended		9 Months Ended	12 Months Ended	3 Months Ended		9 Months Ended		0 Months Ended		1 Months Ended	3 Months Ended		9 Months Ended		12 Months Ended						9 Months Ended		0 Months Ended	1 Months Ended	3 Months Ended		9 Months Ended				1 Months Ended			9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014 Stock options	Sep. 30, 2013 Stock options	Sep. 30, 2014 Stock options	Sep. 30, 2013 Stock options	Dec. 31, 2013 Stock options	Sep. 30, 2014 Stock options Minimum	Sep. 30, 2014 Stock options Maximum	Sep. 30, 2014 Restricted Stock Awards	Dec. 31, 2013 Restricted Stock Awards	Dec. 31, 2012 Restricted Stock Awards	Sep. 30, 2014 LTIP units	Dec. 31, 2013 LTIP units	Sep. 30, 2014 Performance Shares	Sep. 30, 2013 Performance Shares	Sep. 30, 2014 Performance Shares	Sep. 30, 2013 Performance Shares	Dec. 11, 2013 2010 Notional Unit Long-Term Compensation Plan	Dec. 17, 2012 2010 Notional Unit Long-Term Compensation Plan	Dec. 31, 2009 2010 Notional Unit Long-Term Compensation Plan	Sep. 30, 2014 2010 Notional Unit Long-Term Compensation Plan	Sep. 30, 2013 2010 Notional Unit Long-Term Compensation Plan	Sep. 30, 2014 2010 Notional Unit Long-Term Compensation Plan	Sep. 30, 2013 2010 Notional Unit Long-Term Compensation Plan	Dec. 31, 2010 2010 Notional Unit Long-Term Compensation Plan	Dec. 31, 2012 2010 Notional Unit Long-Term Compensation Plan	Dec. 31, 2011 2010 Notional Unit Long-Term Compensation Plan	Dec. 31, 2009 2010 Notional Unit Long-Term Compensation Plan Minimum	Dec. 31, 2009 2010 Notional Unit Long-Term Compensation Plan Maximum	Sep. 30, 2014 Third Amendment and Restated 2005 Stock Option and Incentive Plan fungibleunits	Sep. 30, 2014 Stock options, stock appreciation rights and other awards fungibleunits	Sep. 30, 2014 All other awards fungibleunits	Jun. 30, 2014 2011 Outperformance Plan	Aug. 31, 2011 2011 Outperformance Plan	Sep. 30, 2014 2011 Outperformance Plan	Sep. 30, 2013 2011 Outperformance Plan	Sep. 30, 2014 2011 Outperformance Plan	Sep. 30, 2013 2011 Outperformance Plan	Sep. 30, 2014 2011 Outperformance Plan Vesting on August 31, 2014	Sep. 30, 2014 2011 Outperformance Plan Vesting on August 31, 2015	Sep. 30, 2014 2014 Outperformance Plan	Sep. 01, 2014 2014 Outperformance Plan	Aug. 31, 2014 2014 Outperformance Plan	Sep. 30, 2014 2014 Outperformance Plan Vesting on August 31, 2017	Sep. 30, 2014 2014 Outperformance Plan Vesting on August 31, 2018	Sep. 30, 2014 Deferred Stock Compensation Plan for Directors	Sep. 30, 2014 Employee Stock Purchase Plan	Jan. 01, 2008 Employee Stock Purchase Plan
Third Amended and Restated 2005 Stock Option and Incentive Plan
Maximum fungible units that may be granted (in shares)																																	17,130,000
Fungible units per share (fungible units)																																	2.76	0.77	1.0
Award expiration period										5 years	10 years																							5 years	10 years
Shares that may be issued if equal to fungible units (shares)																																	17,130,000
Number of fungible units available for grant																																	3,200,000.0
Options vesting period										1 year	5 years
Period of commencement of option vesting, from date of grant							1 year
Exercise price of options granted, low end of the range (in dollars per share)							$ 20.67
Exercise price of options granted, high end of the range (in dollars per share)							$ 137.18
Remaining weighted average contractual life of the options outstanding							4 years 2 months 12 days
Remaining weighted average contractual life of the options exercisable							3 years 9 months 4 days
Compensation expense					$ 2,000,000	$ 2,200,000	$ 6,000,000	$ 4,800,000				$ 7,267,923	$ 6,713,155											$ 400,000	$ 900,000	$ 2,300,000	$ 3,600,000											$ 1,700,000	$ 1,700,000	$ 7,800,000	$ 6,200,000
Total unrecognized compensation cost related to unvested stock awards					13,600,000		13,600,000					12,400,000					6,700,000		6,700,000
Weighted average period for recognition of compensation cost related to unvested stock awards							3 years					2 years 1 month 6 days							1 year 2 months 12 days
Stock-based Compensation
Annual award vesting rate, low end of range (as a percent)												15.00%
Annual award vesting rate, high end of range (as a percent)												35.00%
Fair value of restricted stock vested during the period												5,400,000	1,600,000
Cost of the plan, subject to adjustment for forfeitures	1,700,000	900,000	5,200,000	2,900,000																								31,700,000									27,000,000
Weighted average fair value of awards granted during the period							219,823		18,041,576			0	17,386,949		23,600,000	27,100,000
Share-based compensation																	3,400,000	1,900,000	13,700,000	3,500,000
2010 Notional Unit Long-Term Compensation Plan
Approximate amount of LTIP units that may be earned by the recipients based on stock price appreciation																															15,000,000	75,000,000					85,000,000
Stock appreciation period																							3 years														3 years							3 years
Approximate amount of awards that may be earned by recipients after beginning of the second year if maximum performance achieved																							25,000,000
Approximate amount of awards that may be earned by recipients after beginning of the third year if maximum performance achieved																							25,000,000
Minimum stock price appreciation to earn maximum amount of awards (as a percent)																							50.00%
LTIP units earned (in shares)																												366,815	327,416	385,583							560,908									610,000
Percentage of awards, vested or to be vested																					25.00%	50.00%																				50.00%	50.00%				50.00%	50.00%
2011 Outperformance Plan
Value of LTIP Units that could be earned expressed as percentage of outperformance amount in excess of the 25% benchmark (percent)																																					10.00%
Duration period return to stockholders exceeds 25%																																					3 years
Cumulative return to stockholders (percent)																																					25.00%
Maximum LTIP units based on total return to stockholders																																					$ 85,000,000
Award vesting rights after first and second year																																					one-third
Remaining percentage of award to be earned based on performance through the end of the performance period																																					33.33%
Portion of earned LTIP Units vested																																				66.66%
2014 Outperformance Plan
Initial percentage of units to be awarded																																													0.50
Deferred Compensation Plan for Directors
Maximum percentage of the annual retainer fee, chairman fees and meeting fees that may be deferred by non-employee directors (percent)																																																	100.00%
Awards granted (in shares)												0	192,563																																				8,626
Stock units outstanding (in shares)												2,991,763	2,994,197	2,804,901																																			80,137
Employee Stock Purchase Plan
Shares of common stock available for issuance (shares)																																																			500,000
Duration of each offering period starting the first day of each calendar quarter																																																		3 months
Purchase price as a percentage of market value of the common stock (percent)																																																		85.00%
Shares of common stock issued (shares)																																																		78,563