Stock-Based Compensation - Summary of Nonvested Common Share and Common Share Unit Activity (Details) - $ / shares shares in Thousands	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Nonvested shares \| Time and Performance- Based Share Awards
Number of Shares
Outstanding at beginning of year (in shares)	394	482	1,595
Granted (in shares)	109	141	113
Vested (in shares)	(140)	(229)	(1,226)
Forfeited (in shares)	0	0	0
Outstanding at end of period (in shares)	363	394	482
Weighted Average Grant Date Fair Value
Outstanding at beginning of year (in dollars per share)	$ 42.02	$ 29.49	$ 17.03
Granted (in dollars per share)	51.52	45.32	45.02
Vested (in dollars per share)	36.29	17.69	14.71
Outstanding at end of period (in dollars per share)	$ 47.09	$ 42.02	$ 29.49
Nonvested shares \| Time-Based Share Awards
Number of Shares
Outstanding at beginning of year (in shares)	169	207	410
Granted (in shares)	69	90	73
Vested (in shares)	(85)	(128)	(276)
Forfeited (in shares)	0	0	0
Outstanding at end of period (in shares)	153	169	207
Weighted Average Grant Date Fair Value
Outstanding at beginning of year (in dollars per share)	$ 41.31	$ 32.82	$ 21.12
Granted (in dollars per share)	51.52	40.98	45.02
Vested (in dollars per share)	40.47	27.37	18.67
Outstanding at end of period (in dollars per share)	$ 46.34	$ 41.31	$ 32.82
Nonvested share units
Number of Shares
Outstanding at beginning of year (in shares)	351	449	536
Granted (in shares)	350	143	161
Vested (in shares)	(192)	(232)	(238)
Forfeited (in shares)	(17)	(9)	(10)
Outstanding at end of period (in shares)	492	351	449
Weighted Average Grant Date Fair Value
Outstanding at beginning of year (in dollars per share)	$ 39.78	$ 34.35	$ 29.13
Granted (in dollars per share)	48.75	42.08	42.19
Vested (in dollars per share)	37.76	30.85	28.02
Forfeited (in dollars per share)	50.04	35.53	31.59
Outstanding at end of period (in dollars per share)	$ 46.59	$ 39.78	$ 34.35
DEU
Number of Shares
Outstanding at beginning of year (in shares)	5	0
Granted (in shares)	19	5
Vested (in shares)	(3)	0
Forfeited (in shares)	0	0
Outstanding at end of period (in shares)	21	5	0
Weighted Average Grant Date Fair Value
Outstanding at beginning of year (in dollars per share)	$ 51.11
Granted (in dollars per share)	35.42	$ 51.09
Vested (in dollars per share)	49.79	48.63
Forfeited (in dollars per share)	33.86	49.27
Outstanding at end of period (in dollars per share)	$ 37.66	$ 51.11

The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period.

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Weighted average fair value as of the grant date of equity-based award plans other than stock (unit) option plans that were not exercised or put into effect as a result of the occurrence of a terminating event.

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The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Per share or unit weighted-average fair value of nonvested award under share-based payment arrangement. Excludes share and unit options.

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The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

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The weighted average fair value as of grant date pertaining to an equity-based award plan other than a stock (or unit) option plan for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement.

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