Partners' Capital, Equity and Incentive Compensation Plans - Summary of Assumptions and Fair Values for Restricted Stock and Options to Purchase Shares of Class A Common Stock Granted (Detail) (USD $)	3 Months Ended	6 Months Ended
	Jun. 30, 2014	Jun. 30, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of restricted stock granted	$ 25.51	$ 25.51
Expected volatility	33.00%	33.00%
Expected dividend yield	4.55%	4.55%
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of options granted	$ 4.94	$ 4.94
Expected term (years)	5 years 6 months	5 years 6 months
Expected risk-free interest rates	1.70%	1.70%
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of options granted	$ 5.08	$ 5.08
Expected term (years)	6 years 1 month 6 days	6 years 1 month 6 days
Expected risk-free interest rates	1.90%	1.90%