Share-Based Compensation - Summary of Restricted Stock and Performance Units Activity (Details) - $ / shares		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Restricted Stock
Restricted Stock and Performance Units [Roll Forward]
Outstanding at January 1		716,952	743,591	739,732
Granted		204,960	199,499	173,144
Vested	[1]	(244,823)	(212,809)	(165,547)
Forfeitures		(7,987)	(13,329)	(3,738)
Outstanding at December 31		669,102	716,952	743,591
Restricted Stock and Performance Units (Weighted Average Grant-date Fair Value) [Abstract]
Weighted Average Grant-Date Fair Value, Outstanding at January 1		$ 94.50	$ 86.90	$ 77.23
Weighted Average Grant-Date Fair Value, Granted		94.25	95.48	114.63
Weighted Average Grant-Date Fair Value, Vested	[1]	72.11	68.59	72.84
Weighted Average Grant-Date Fair Value, Forfeitures		99.94	98.86	78.66
Weighted Average Grant-Date Fair Value, Outstanding at December 31		$ 102.55	$ 94.50	$ 86.90
Performance Units
Restricted Stock and Performance Units [Roll Forward]
Outstanding at January 1		323,147	266,704	226,558
Granted		111,287	109,545	83,515
Vested	[2]	(77,017)	(53,102)	(43,369)
Outstanding at December 31		357,417	323,147	266,704
Restricted Stock and Performance Units (Weighted Average Grant-date Fair Value) [Abstract]
Weighted Average Grant-Date Fair Value, Outstanding at January 1		$ 96.56	$ 90.01	$ 77.07
Weighted Average Grant-Date Fair Value, Granted		99.20	97.24	115.35
Weighted Average Grant-Date Fair Value, Vested	[2]	67.57	65.03	71.19
Weighted Average Grant-Date Fair Value, Outstanding at December 31		$ 103.63	$ 96.56	$ 90.01

[1] The total fair value of awards upon vesting for the years ended December 31, 2020, 2019, and 2018 was $23.6 million, $19.9 million, and $18.9 million, respectively.

[2] The total fair value of awards upon vesting for the years ended December 31, 2020, 2019, and 2018 was $8.5 million, $5.5 million, and $5.4 million, respectively. Upon vesting of the awards in 2020, 2019, and 2018, PCA issued 86,015 shares, 59,165 shares, and 46,876 shares, respectively. For 2020, 2019, and 2018, these amounts included 8,998 shares, 6,063 shares, and 3,507 shares, respectively, for dividends accrued during the vesting period.