Equity Based Compensation Plans - Restricted Stock Activity and LITP Units (Details) - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Restricted Stock
Total Unvested Units
Unvested at beginning of year (in shares)	132,603	114,877	91,058	90,823
Granted (in shares)	45,196	41,643	51,945
Vested (in shares)	(15,116)	(13,222)	(48,212)
Forfeited and canceled (in shares)	(12,354)	(4,602)	(3,498)
Unvested at end of year (in shares)	132,603	114,877	91,058	90,823
Weighted- average grant price
Unvested at beginning of year (in dollars per share)	$ 197.62	$ 180.99	$ 163.49
Granted (in dollars per share)	248.16	235.93	194.70
Vested (in dollars per share)	170.61	143.56	150.76
Forfeited and canceled (in dollars per share)	184.11	158.06	158.71
Unvested at end of year (in dollars per share)	$ 214.34	$ 197.62	$ 180.99	$ 163.49
Long Term Incentive Plans - Z Units and 2014 LTIP Units
Total Unvested Units
Unvested at beginning of year (in shares)	0	1,890	11,161	23,212
Granted (in shares)	0	0	0
Vested (in shares)	(1,890)	(9,176)	(12,051)
Converted (in shares)	0	0	0
Forfeited and canceled (in shares)	0	(95)	0
Unvested at end of year (in shares)	0	1,890	11,161	23,212
Weighted- average grant price
Unvested at beginning of year (in dollars per share)	$ 75.03	$ 75.03	$ 75.03
Unvested at end of year (in dollars per share)	$ 84.47	$ 75.03	$ 75.03	$ 75.03
Total Vested Units
Vested, beginning balance (in shares)	143,257	134,081	213,300
Vested, units granted (in shares)	0	0	0
Vested, units vested (in shares)	1,890	9,176	12,051
Converted (in shares)	(39,010)	0	(91,270)
Cancelled (in shares)	0	0	0
Vested, ending balance (in shares)	106,137	143,257	134,081	213,300
Total Outstanding Units
Total outstanding units, beginning balance (in shares)	145,147	145,242	236,512
Total outstanding units, granted (in shares)	0	0	0
Total outstanding units, vested (in shares)	0	0	0
Total outstanding units, converted (in shares)	(39,010)	0	(91,270)
Total outstanding units, cancelled (in shares)	0	(95)	0
Total outstanding units, ending balance (in shares)	106,137	145,147	145,242	236,512
Weighted- average Remaining Contractual Life (years)	3 years 7 months 6 days	5 years 2 months 12 days	6 years 6 months	7 years 6 months