Capital Stock (Details) $ / shares in Units, $ in Millions	1 Months Ended
	Nov. 30, 2014 USD ($) $ / shares shares	Nov. 30, 2013 USD ($) vote $ / shares shares	Dec. 31, 2015 shares	Dec. 31, 2014 shares	Nov. 05, 2013 shares
Capital Stock
Authorized share capital			233,333,000	233,333,000	233,300,000
Share split ratio		0.6666
Number of votes per share | vote		1
Shareholder ownership threshold for voting rights (as a percent)		9.50%
Maximum number of votes per share for certain shareholders under 9.5% shareholder provision | vote		1
Minimum number of votes per share for other shareholders under 9.5% shareholder provision | vote		1
Class A Common Shares
Capital Stock
Dividend rate, as a percentage of issue price per annum		10.00%
Conversion of a class of shares into a single class of common shares | 2009 Restricted Share Plan | Class A and Class B-2 Common Shares
Capital Stock
Number of new shares issued upon conversion of stock		64,700,000
IPO
Capital Stock
Shares issued (in shares)		20,000,000
Share price (in dollars per share) | $ / shares		$ 17.00
Shares sold by selling shareholders		2,700,000
Net proceeds from sale of stock | $		$ 313.7
Public offering
Capital Stock
Shares issued (in shares)	6,000,000.0
Share price (in dollars per share) | $ / shares	$ 22.25
Shares sold by selling shareholders	7,800,000
Net proceeds from sale of stock | $	$ 126.7