Equity Based Compensation Plans, Restricted stock activity (Details) - $ / shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Restricted Stock [Member]
Shares [Roll forward]
Unvested at beginning of year (in shares)	25,820	16,176	24,922
Granted (in shares)	56,177	22,014	1,556
Assumed - Merger (in shares)	0	119,411	0
Vested (in shares)	(22,939)	(126,931)	(7,211)
Forfeited and canceled (in shares)	(4,382)	(4,850)	(3,091)
Unvested at end of year (in shares)	54,676	25,820	16,176	24,922
Weighted-average grant price [Abstract]
Unvested at beginning of year (in dollars per share)	$ 168.22	$ 108.06	$ 104.52
Granted (in dollars per share)	155.21	194.03	158.75
Assumed - Merger (in dollars per share)	0.00	173.82	0.00
Vested (in dollars per share)	148.20	171.56	109.86
Forfeited and canceled (in dollars per share)	122.06	135.10	100.84
Unvested at end of year (in dollars per share)	$ 147.10	$ 168.22	$ 108.06	$ 104.52
Long Term Incentive Plans - Z Units and 2014 LTIP Units [Member]
Shares [Roll forward]
Unvested at beginning of year (in shares)	151,067	149,381	140,043
Granted (in shares)	0	44,750	50,500
Vested (in shares)	36,650	41,729	35,919
Converted (in shares)	0	0	0
Forfeited and canceled (in shares)	(8,260)	(1,335)	(5,243)
Unvested at end of year (in shares)	106,157	151,067	149,381	140,043
Weighted-average grant price [Abstract]
Unvested at beginning of year (in dollars per share)	$ 71.14	$ 63.53	$ 58.44
Unvested at end of year (in dollars per share)	$ 75.41	$ 71.14	$ 63.53	$ 58.44
Incentive units vested [Roll Forward]
Vested, beginning balance (in shares)	181,919	118,190	190,704
Vested, units granted (in shares)	0	24,000	0
Vested, units vested (in shares)	36,650	41,729	35,919
Converted (in shares)	(74,384)	(2,000)	(108,433)
Cancelled (in shares)	0	0	0
Vested, ending balance (in shares)	144,185	181,919	118,190	190,704
Total outstanding incentive units [Abstract]
Total outstanding units, beginning balance (in shares)	332,986	267,571	330,747
Total outstanding units, granted (in shares)	0	68,750	50,500
Total outstanding units, vested (in shares)	0	0	0
Total outstanding units, converted (in shares)	(74,384)	(2,000)	(108,433)
Total outstanding units, cancelled (in shares)	(8,260)	(1,335)	(5,243)
Total outstanding units, ending balance (in shares)	250,342	332,986	267,571	330,747
Weighted average remaining contractual life outstanding units	9 years 6 months	10 years 6 months	9 years 3 months 24 days	11 years 3 months 24 days