Capital Stock and Share Based Compensation Plans - Narrative (Details) $ / shares in Units, $ in Thousands	1 Months Ended	12 Months Ended			24 Months Ended
	Dec. 31, 2016 USD ($) director common_share shares	Dec. 31, 2016 USD ($) director common_share $ / shares shares	Dec. 31, 2015 USD ($) $ / shares	Dec. 31, 2014 USD ($)	Dec. 31, 2016 USD ($) director common_share shares	Nov. 30, 2016 USD ($)	May 31, 2014 USD ($)
Class of Stock [Line Items]
Classes of common shares | common_share	2	2			2
Minimum number of directors up for election to entitle shareholders to vote | director	3	3			3
Minumum percent of directors up for election to entitle shareholders to vote	33.33%	33.33%			33.33%
Stock repurchased during period, value		$ 44,401	$ 16,222	$ 21,237
Number of shares available for future stock compensation grants | shares	4,500,000.0	4,500,000.0			4,500,000.0
Total unrecognized compensation cost related to restricted stock, RSUs and performance shares	$ 7,500	$ 7,500			$ 7,500
Stock Options | Common stock, Class A | Maximum
Class of Stock [Line Items]
Purchase price of stock options granted, percent of fair market value		100.00%
Restricted Stock Units (RSUs)
Class of Stock [Line Items]
Weighted-average period of recognition, years		2 years 3 months
Restricted Stock Units (RSUs) | Minimum
Class of Stock [Line Items]
Vesting period of stock options		3 years
Restricted Stock Units (RSUs) | Maximum
Class of Stock [Line Items]
Vesting period of stock options		4 years
First Repurchase Plan | Minimum
Class of Stock [Line Items]
Range of price of shares repurchased | $ / shares		$ 12.84	$ 15.92
First Repurchase Plan | Maximum
Class of Stock [Line Items]
Range of price of shares repurchased | $ / shares		$ 19.51	$ 24.96
First Repurchase Plan | Common stock, Class A
Class of Stock [Line Items]
Stock repurchase program, authorized amount							$ 100,000
Stock repurchased during period, value	$ 1,000		$ 16,000		$ 44,000
Second Repurchase Plan | Common stock, Class A
Class of Stock [Line Items]
Stock repurchase program, authorized amount						$ 100,000
Stock repurchased during period, value		$ 0