Share and Unit-Based Plans - Nonvested equity awards (Details)	3 Months Ended
	Mar. 31, 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)	0
Balance at end of period (in shares)	1,165,677
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	0
Balance at end of period (in dollars per share) | $ / shares	$ 33.06
Phantom Stock Units
Units
Balance at beginning of period (in shares)	7,216
Granted (in shares)	12,637
Vested (in shares)	(6,881)
Forfeited (in shares)	0
Balance at end of period (in shares)	12,972
Value
Balance at beginning of period (in dollars per share) | $ / shares	$ 43.29
Granted (in dollars per share) | $ / shares	25.02
Vested (in dollars per share) | $ / shares	27.12
Forfeited (in dollars per share) | $ / shares	0
Balance at end of period (in dollars per share) | $ / shares	$ 34.06
Stock Units
Units
Balance at beginning of period (in shares)	199,987
Granted (in shares)	120,913
Vested (in shares)	(63,849)
Forfeited (in shares)	0
Balance at end of period (in shares)	257,051
Value
Balance at beginning of period (in dollars per share) | $ / shares	$ 43.59
Granted (in dollars per share) | $ / shares	19.45
Vested (in dollars per share) | $ / shares	52.39
Forfeited (in dollars per share) | $ / shares	0
Balance at end of period (in dollars per share) | $ / shares	$ 30.05