Stockholders’ Equity and Earnings Per Share (Narrative) (Details) - USD ($)	3 Months Ended												12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jan. 17, 2014	Jan. 16, 2014	Jul. 17, 2013
Quarterly Dividends
Dividends declared per common share (in dollars per share)	$ 0.23	$ 0.23	$ 0.20	$ 0.20	$ 0.20	$ 0.20	$ 0.20	$ 0.20					$ 0.86	$ 0.80	$ 0.80
Total cash dividends declared													$ 126,000,000	$ 117,000,000	$ 116,600,000
Common Stock
Class of Stock
Amount of stock repurchase authorized by the Board of Directors																		$ 100,000,000
Purchase of treasury stock pursuant to the Stock Repurchase Program (in shares)													0	0
Warrant
Shares of common stock into which the warrant may be converted (in shares)																230,282
Quarterly Dividends
Dividends declared per common share (in dollars per share)	$ 0.23	$ 0.23	$ 0.20	$ 0.20	$ 0.20	$ 0.20	$ 0.20	$ 0.20	$ 0.20	$ 0.20	$ 0.20	$ 0.20
MetroCorp | MetroCorp
Warrant
Shares of common stock into which the warrant may be converted (in shares)																	771,429