Share-Based and Other Deferred Compensation - Additional information (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended		3 Months Ended			6 Months Ended				0 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013 Deferred Cash Program [Member]	Jun. 30, 2012 Deferred Cash Program [Member]	Mar. 31, 2011 Deferred Cash Program [Member] Y	Jun. 30, 2013 Deferred Cash Program [Member]	Jun. 30, 2012 Deferred Cash Program [Member]	Jun. 30, 2013 Minimum [Member]	Jun. 30, 2013 Maximum [Member]	Jul. 23, 2013 Subsequent Event [Member] Long Term Incentive Plan [Member] Y
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Service based awards granted (in shares)			2,193
Service based awards, grant date fair value (in dollars per share)										$ 26.60	$ 43.26
Service based awards vested (in shares)			1,870
Service based awards forfeited (in shares)			44
Deferred compensation, vesting period (in years)							4
Compensation expense related to deferred compensation program					$ 838	$ 1,281		$ 1,829	$ 2,265
Compensation expense related to service-based awards	20,634	16,038	41,227	30,699
Compensation expense related to amortization of LP units	4,813	5,069	10,423	9,828
Compensation expense related to acquisition related awards	3,618	4,379	7,226	10,632
Compensation expense related to deferred cash consideration	$ 1,214	$ 1,751	$ 2,263	$ 4,621
Additional shares to be granted under stock incentive plan	5,000
Long Term Incentive Plan Performance Period (in years)												4
Long Term Incentive Plan Payment Period (in years)												2