Performance Incentive Plan (Restricted Stock Activity) (Details)	12 Months Ended
	Dec. 31, 2019 $ / shares shares
Number of Shares
Restricted shares granted (in shares) | shares	28,127
Weighted Average Share Price
Restricted shares granted (in dollars per share) | $ / shares	$ 53.47
Restricted stock
Number of Shares
Non-vested restricted shares, January 1 (in shares) | shares	781,564
Restricted shares granted (in shares) | shares	364,769
Restricted shares vested (in shares) | shares	(237,863)
Restricted shares forfeited (in shares) | shares	(5,119)
Non-vested restricted shares, December 31 (in shares) | shares	903,351
Weighted Average Share Price
Non-vested restricted shares, January 1 (in dollars per share) | $ / shares	$ 39.97
Restricted shares granted (in dollars per share) | $ / shares	53.91
Restricted shares vested (in dollars per share) | $ / shares	43.03
Restricted shares forfeited (in dollars per share) | $ / shares	44.70
Non-vested restricted shares, December 31 (in dollars per share) | $ / shares	$ 44.77