Stock Compensation Plans (Summary of Activity for Time-Based and Performance-Based RSUs) (Details)	6 Months Ended
	Jun. 30, 2021 $ / shares shares
Time-Based RSUs Settled in Shares
Shares
Outstanding, at beginning of period (in shares)	1,345,635
Granted (in shares)	382,359
Vested (in shares)	(285,513)
Forfeited (in shares)	(65,648)
Outstanding, at end of period (in shares)	1,376,833
Weighted-Average Grant Date Fair Value
Outstanding, at beginning of period (in dollars per share) | $ / shares	$ 50.22
Granted (in dollars per share) | $ / shares	71.41
Vested (in dollars per share) | $ / shares	67.26
Forfeited (in dollars per share) | $ / shares	56.26
Outstanding, at end of period (in dollars per share) | $ / shares	$ 52.28
Performance-Based RSUs Settled in Shares
Shares
Outstanding, at beginning of period (in shares)	398,057
Granted (in shares)	91,960
Vested (in shares)	(120,286)
Forfeited (in shares)	0
Outstanding, at end of period (in shares)	369,731
Weighted-Average Grant Date Fair Value
Outstanding, at beginning of period (in dollars per share) | $ / shares	$ 53.66
Granted (in dollars per share) | $ / shares	77.67
Vested (in dollars per share) | $ / shares	70.13
Forfeited (in dollars per share) | $ / shares	0
Outstanding, at end of period (in dollars per share) | $ / shares	$ 54.28
Time-Based RSUs Settled in Cash
Shares
Outstanding, at beginning of period (in shares)	21,802
Granted (in shares)	15,803
Vested (in shares)	0
Forfeited (in shares)	(8,432)
Outstanding, at end of period (in shares)	29,173