Stockholders' Equity (Schedule of Deferred Stock Units Transactions) (Details) - Deferred Stock Unit - $ / shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Number of Shares
Balance at beginning of the period (in shares)	527,513	738,288	692,961
Issued (in shares)	10,742	54,982	56,212
Granted (in shares)	173,097	90,184	187,490
Dividend equivalents (in shares)	9,075	20,922	27,532
Forfeited (in shares)	(10,893)	(23,604)	(38,855)
Exercised (in shares)	(203,087)	(353,259)	(187,052)
Balance at end of the period (in shares)	506,447	527,513	738,288
Outstanding exercise price (in usd per share)	$ 44.94	$ 36.96	$ 30.26
Issued (in usd per share)	72.01	47.51	46.08
Granted (in usd per share)	54.67	60.22	46.94
Dividend equivalent (in usd per share)	87.01	59.94	50.45
Forfeited (in usd per share)	48.98	44.78	29.83
Exercised (in usd per share)	43.55	32.62	29.90
Outstanding exercise price (in usd per share)	$ 50.00	$ 44.94	$ 36.96