Stockholders' Equity (Schedule of Deferred and Restricted Stock Units Transactions) (Details) - Deferred and Restricted Stock Unit - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Number of Shares
Balance at beginning of the period (in shares)	346,148	264,406	449,055
Issued (in shares)	5,703	6,073	5,354
Granted (in shares)	150,319	252,068	101,650
Dividend equivalents (in shares)	10,042	10,243	8,036
Forfeited (in shares)	(21,856)	(9,079)	(9,557)
Vested (in shares)	(155,269)	(177,563)	(290,132)
Balance at end of the period (in shares)	335,087	346,148	264,406
Weighted Average Price
Outstanding exercise price (in usd per share)	$ 87.54	$ 83.84	$ 72.55
Issued (in usd per share)	97.42	89.82	106.10
Granted (in usd per share)	97.70	81.07	103.20
Dividend equivalent (in usd per share)	95.08	89.65	89.66
Forfeited (in usd per share)	91.79	89.67	76.71
Exercised (in usd per share)	87.69	69.65	74.83
Outstanding exercise price (in usd per share)	$ 90.04	$ 87.54	$ 83.84