Share and Unit-Based Plans - Nonvested equity awards (Details)	9 Months Ended
	Sep. 30, 2019 $ / shares shares
LTIP Units
Units
Balance at beginning of period (in shares) | shares	661,578
Granted (in shares) | shares	343,431
Vested (in shares) | shares	(7,654)
Forfeited (in shares) | shares	(14,635)
Balance at end of period (in shares) | shares	982,720
Value
Balance at beginning of period (in dollars per share) | $ / shares	$ 48.38
Granted (in dollars per share) | $ / shares	32.40
Vested (in dollars per share) | $ / shares	59.85
Forfeited (in dollars per share) | $ / shares	34.26
Balance at end of period (in dollars per share) | $ / shares	$ 42.91
Phantom Stock Units
Units
Balance at beginning of period (in shares) | shares	0
Granted (in shares) | shares	21,580
Vested (in shares) | shares	(12,756)
Forfeited (in shares) | shares	0
Balance at end of period (in shares) | shares	8,824
Value
Balance at beginning of period (in dollars per share) | $ / shares	$ 0
Granted (in dollars per share) | $ / shares	41.61
Vested (in dollars per share) | $ / shares	42.87
Forfeited (in dollars per share) | $ / shares	0
Balance at end of period (in dollars per share) | $ / shares	$ 39.79
Stock Units
Units
Balance at beginning of period (in shares) | shares	129,457
Granted (in shares) | shares	159,116
Vested (in shares) | shares	(83,341)
Forfeited (in shares) | shares	(5,245)
Balance at end of period (in shares) | shares	199,987
Value
Balance at beginning of period (in dollars per share) | $ / shares	$ 64.21
Granted (in dollars per share) | $ / shares	37.57
Vested (in dollars per share) | $ / shares	63.63
Forfeited (in dollars per share) | $ / shares	51.48
Balance at end of period (in dollars per share) | $ / shares	$ 43.59