Common Stock (Details) - USD ($)	1 Months Ended	3 Months Ended	12 Months Ended			60 Months Ended
	Dec. 31, 2013	Dec. 31, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2015	Oct. 28, 2015	Oct. 23, 2014	Dec. 05, 2013	Sep. 26, 2011
Equity, Class of Treasury Stock [Line Items]
Common stock, outstanding (in shares)		61,067,868	61,067,868	62,981,229		61,067,868
Increase in quarterly dividend declared (in dollars per share)	$ 0.08
Dividend paid (in dollars per share)		$ 0.08
Stock repurchased (in US dollars)			$ 112,328,000	$ 206,028,000	$ 26,070,000
Common Stock
Equity, Class of Treasury Stock [Line Items]
Number of shares repurchased (in shares)						9,900,000
Stock repurchased (in US dollars)			24,000	$ 48,000	$ 7,000	$ 395,900,000
Remaining authorized repurchase amount (in US dollars)		$ 254,100,000	$ 254,100,000			$ 254,100,000
Common Stock | RepurchaseProgramSept262011
Equity, Class of Treasury Stock [Line Items]
Stock repurchase, authorized amount (in US dollars)										$ 100,000,000
Number of shares repurchased (in shares)			2,300,000
Stock repurchased (in US dollars)			$ 112,300,000
Common Stock | RepurchaseProgramDec52013
Equity, Class of Treasury Stock [Line Items]
Stock repurchase, authorized amount (in US dollars)									$ 100,000,000
Common Stock | RepurchaseProgramOct232014
Equity, Class of Treasury Stock [Line Items]
Stock repurchase, authorized amount (in US dollars)								$ 250,000,000
Common Stock | RepurchaseProgramOct282015
Equity, Class of Treasury Stock [Line Items]
Stock repurchase, authorized amount (in US dollars)							$ 200,000,000