Partners' Capital, Equity and Incentive Compensation Plans (Summary of Award Activity Under 2010 Equity Incentive Plan and 2013 Equity Incentive Plan and Related Information) (Details) - $ / shares		9 Months Ended	12 Months Ended
		Sep. 30, 2015	Dec. 31, 2014
2013 Equity Incentive Plan [Member] | Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Beginning balance, Weighted average fair value		$ 4.10
Weighted average fair value, Granted		8.03
Weighted average fair value, Exercised	[1]	$ 3.71
Weighted average fair value, Released from restriction	[2]
Weighted average fair value, Cancelled/Expired	[3]	$ 3.52
Ending balance, Weighted average fair value		$ 5.53	$ 4.10
Options, Granted		(317,497)	584,949
Options, Exercised	[1]	(12,780)
Options, Released from restriction	[2]
Options, Cancelled/Expired	[3]	(11,407)
Ending balance, Options Outstanding		878,259
Beginning balance, Weighted average exercise price options outstanding		$ 22.87
Weighted average exercise price options outstanding, Granted		36.16
Weighted average exercise price options outstanding, Exercised	[1]	$ 21.55
Weighted average exercise price options outstanding, Released from restriction	[2]
Weighted average exercise price options outstanding, Cancelled/Expired	[3]	$ 21.00
Ending balance, Weighted average exercise price options outstanding		$ 27.72	$ 22.87
2013 Equity Incentive Plan [Member] | Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Beginning balance, Number of units		246,785
Number of units, granted		231,722
Number of units, Exercised	[1]	(27,341)
Number of units, Released from restriction	[2]
Number of units, Cancelled/Expired	[3]	(12,278)
Ending balance, Number of units		438,888	246,785
Beginning balance, Weighted average fair value		$ 29.13
Weighted average fair value, Granted		36.72
Weighted average fair value, Exercised	[1]	$ 22.99
Weighted average fair value, Released from restriction	[2]
Weighted average fair value, Cancelled/Expired	[3]	$ 23.64
Ending balance, Weighted average fair value		33.67	$ 29.13
2010 Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Beginning balance, Weighted average exercise price units		$ 23.49
Weighted average exercise price units, Granted
Weighted average exercise price units, Exercised	[1]	$ 21.78
Weighted average exercise price units, Released from restriction	[2]
Weighted average exercise price units, Cancelled/Expired	[3]
Ending balance, Weighted average exercise price units		$ 23.56	23.49
Beginning balance, Weighted average fair value		$ 3.75
Weighted average fair value, Granted
Weighted average fair value, Exercised	[1]	$ 5.04
Weighted average fair value, Released from restriction	[2]
Weighted average fair value, Cancelled/Expired	[3]
Ending balance, Weighted average fair value		$ 3.70	3.75
Beginning balance, Weighted average exercise price options outstanding		$ 23.49
Weighted average exercise price options outstanding, Granted
Weighted average exercise price options outstanding, Exercised	[1]
Weighted average exercise price options outstanding, Released from restriction	[2]	$ 25.00
Weighted average exercise price options outstanding, Cancelled/Expired	[3]
Ending balance, Weighted average exercise price options outstanding		$ 22.68	$ 23.49
Restricted Class A Common Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Units surrendered		12,278
Class O Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Ending balance, Number of units		500,000
Class O Units [Member] | 2010 Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Beginning balance, Number of units		1,518,717
Number of units, granted
Number of units, Exercised	[1]	(55,066)
Number of units, Released from restriction	[2]
Number of units, Cancelled/Expired	[3]
Ending balance, Number of units		1,463,651	1,518,717
Class RS Units [Member] | 2010 Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Beginning balance, Options Outstanding		74,625
Options, Granted
Options, Exercised	[1]
Options, Released from restriction	[2]	(26,062)
Options, Cancelled/Expired	[3]
Ending balance, Options Outstanding		48,563	74,625

[1] This represents the Class A common stock that has been released from restriction and which was not surrendered by the holder to satisfy their statutory minimum federal and state tax obligations associated with the vesting of restricted common stock.

[2] This represents Class RS units that upon vesting have converted to Operating Partnership units.

[3] Includes 12,278 restricted Class A common stock surrendered by certain employees to satisfy their statutory minimum federal and state tax obligations associated with the vesting of restricted common stock.