Share and Unit-Based Plans - Nonvested equity awards (Details)	6 Months Ended
	Jun. 30, 2020 $ / shares shares
Units
Granted (in shares)	552,866
LTIP Units
Units
Balance at beginning of period (in shares)	616,219
Granted (in shares)	552,866
Vested (in shares)	(3,408)
Forfeited (in shares)	(6,714)
Balance at end of period (in shares)	1,158,963
Value
Balance at beginning of period (in dollars per share) | $ / shares	$ 39.04
Granted (in dollars per share) | $ / shares	26.59
Vested (in dollars per share) | $ / shares	66.02
Forfeited (in dollars per share) | $ / shares	39.66
Balance at end of period (in dollars per share) | $ / shares	$ 33.02
Phantom Stock Units
Units
Balance at beginning of period (in shares)	7,216
Granted (in shares)	17,836
Vested (in shares)	(15,825)
Forfeited (in shares)	0
Balance at end of period (in shares)	9,227
Value
Balance at beginning of period (in dollars per share) | $ / shares	$ 43.29
Granted (in dollars per share) | $ / shares	20.23
Vested (in dollars per share) | $ / shares	22.32
Forfeited (in dollars per share) | $ / shares	0
Balance at end of period (in dollars per share) | $ / shares	$ 34.67
Stock Units
Units
Balance at beginning of period (in shares)	199,987
Granted (in shares)	247,872
Vested (in shares)	(100,076)
Forfeited (in shares)	(399)
Balance at end of period (in shares)	347,384
Value
Balance at beginning of period (in dollars per share) | $ / shares	$ 43.59
Granted (in dollars per share) | $ / shares	14.24
Vested (in dollars per share) | $ / shares	45.18
Forfeited (in dollars per share) | $ / shares	59.04
Balance at end of period (in dollars per share) | $ / shares	$ 22.17