Stock Equivalent Units (Details) - $ / shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Equity Instruments Other than Options Activity [Roll Forward]
Balance at January 1 (in shares)	939,000
Granted (in shares)	483,000	500,000	503,000
Dividend equivalents (in shares)	38,000
Balance at December 31 (in shares)	880,000	939,000
Equity Instruments Other than Options, Weighted Average Grant Date Fair Value [Abstract]
Balance at January 1, weighted average grant date fair value (in dollars per share)	$ 44.30
Granted, weighted average grant date fair value (in dollars per share)	49.67	$ 47.60	$ 41.02
Dividend equivalents, weighted average grant date fair value (in dollars per share)	45.22
Balance at December 31, weighted average grant date fair value (in dollars per share)	$ 48.20	$ 44.30
Stock Equivalent Units [Member]
Equity Instruments Other than Options Activity [Roll Forward]
Balance at January 1 (in shares)	688,000
Granted (in shares)	29,000	36,000	51,000
Units distributed (in shares)	(11,000)
Dividend equivalents (in shares)	19,000
Balance at December 31 (in shares)	725,000	688,000
Equity Instruments Other than Options, Weighted Average Grant Date Fair Value [Abstract]
Balance at January 1, weighted average grant date fair value (in dollars per share)	$ 30.93
Granted, weighted average grant date fair value (in dollars per share)	58.44	$ 45.44	$ 46.05
Units distributed, weighted average grant date fair value (in dollars per share)	32.56
Dividend equivalents, weighted average grant date fair value (in dollars per share)	57.28
Balance at December 31, weighted average grant date fair value (in dollars per share)	$ 32.72	$ 30.93
Equity Instruments Other than Options, Additional Disclosures [Abstract]
Number of shares of common stock into which the share-based compensation can be converted (in shares)	1