Shareholders' Equity (Schedule of Stock by Class) (Details)	3 Months Ended						9 Months Ended
	Sep. 30, 2015 vote stockclass $ / shares shares	Jun. 30, 2015 $ / shares	Mar. 31, 2015 $ / shares	Sep. 30, 2014 $ / shares	Jun. 30, 2014 $ / shares	Mar. 31, 2014 $ / shares	Sep. 30, 2015 vote stockclass $ / shares shares	Sep. 30, 2014 $ / shares	Dec. 31, 2014 $ / shares shares
Class of Stock [Line Items]
Classes of common stock | stockclass	3						3
Preferred stock, authorized shares	500,000.0						500,000.0		500,000
Preferred stock, par value (USD per share) | $ / shares	$ 0.01						$ 0.01		$ 0.01
Preferred stock, issued shares	0						0		0
Dividends declared per share (USD per share) | $ / shares	$ 0.30	$ 0.30	$ 0.30	$ 0.30	$ 0.30	$ 0.30	$ 0.90	$ 0.90
Class A stock [Member]
Class of Stock [Line Items]
Authorized Shares	80,000,000						80,000,000		80,000,000
Common stock, par value (USD per share) | $ / shares	$ 0.025						$ 0.025		$ 0.025
Votes per share | vote	1						1
Class B stock [Member]
Class of Stock [Line Items]
Authorized Shares	80,000,000						80,000,000		80,000,000
Common stock, par value (USD per share) | $ / shares	$ 0.025						$ 0.025		$ 0.025
Votes per share | vote	10						10
Class C stock [Member]
Class of Stock [Line Items]
Authorized Shares	20,000,000						20,000,000		20,000,000
Common stock, par value (USD per share) | $ / shares	$ 0.025						$ 0.025		$ 0.025
Votes per share | vote	10						10
Common Stock [Member] | Class A stock [Member]
Class of Stock [Line Items]
Issued Common Stock	40,000,000						40,000,000		40,000,000
Common Stock [Member] | Class B stock [Member]
Class of Stock [Line Items]
Issued Common Stock	15,000,000						15,000,000		15,000,000
Common Stock [Member] | Class C stock [Member]
Class of Stock [Line Items]
Issued Common Stock	500,000						500,000		500,000
Outstanding [Member] | Class A stock [Member]
Class of Stock [Line Items]
Issued Common Stock	35,400,000						35,400,000		34,700,000
Outstanding [Member] | Class B stock [Member]
Class of Stock [Line Items]
Issued Common Stock	14,200,000						14,200,000		14,200,000
Outstanding [Member] | Class C stock [Member]
Class of Stock [Line Items]
Issued Common Stock	0						0		0
Treasury [Member] | Class A stock [Member]
Class of Stock [Line Items]
Issued Common Stock	4,600,000						4,600,000		5,300,000
Treasury [Member] | Class B stock [Member]
Class of Stock [Line Items]
Issued Common Stock	800,000						800,000		800,000
Treasury [Member] | Class C stock [Member]
Class of Stock [Line Items]
Issued Common Stock	500,000						500,000		500,000